Cuando terminemos de comer, pasaremos la mopa por el suelo y luego la bayeta por la mesa de la cocina.

Because cuando refers to a future action here: when we finish eating.

In Spanish, when cuando introduces a future event, the verb in that clause usually goes in the present subjunctive:

• Cuando terminemos de comer... = When we finish eating...

If you say cuando terminamos, that normally refers to a habitual action or a past context depending on the sentence:

• Cuando terminamos de comer, siempre recogemos la mesa. = When we finish eating, we always clear the table.

So in your sentence, terminemos is used because the speaker is talking about something that will happen later.

Because terminar de + infinitive is a very common Spanish structure meaning to finish doing something.

So:

• terminar de comer = to finish eating
• terminar de limpiar = to finish cleaning
• terminar de estudiar = to finish studying

In this sentence, Cuando terminemos de comer literally means When we finish eating.

Be careful: terminar on its own often means to end or to finish, but if you want to say what activity is being finished, de + infinitive is the normal pattern.

Because the sentence is talking about what we will do after finishing the meal.

• pasaremos la mopa... = we will run the mop / we will mop...

Spanish often uses the simple future for planned or expected future actions, especially in neutral written or careful spoken language.

You could also hear other natural options in conversation, such as:

• Cuando terminemos de comer, vamos a pasar la mopa...
• Cuando terminemos de comer, pasamos la mopa... (present used with future meaning in some contexts)

But pasaremos is completely correct and natural.

Because Spanish usually drops subject pronouns when the verb ending already shows who is doing the action.

• terminemos already tells you it means we
• pasaremos also clearly means we

So nosotros is unnecessary unless the speaker wants emphasis or contrast:

• Nosotros pasaremos la mopa, y ellos fregarán los platos.

In normal Spanish, leaving out the pronoun is the most natural choice.

Pasar la mopa is a common expression in Spain meaning to mop or more literally to run a mop over the floor.

The verb pasar often means to pass, but in cleaning contexts it can mean to move something over a surface:

• pasar la mopa = run the mop over the floor
• pasar la aspiradora = vacuum
• pasar un trapo = wipe with a cloth

So here pasaremos la mopa por el suelo means we’ll mop the floor.

Because the pattern is:

pasar + object + por + surface

So:

• pasar la mopa por el suelo
• pasar la bayeta por la mesa

The cleaning tool is the direct object, and the place/surface is introduced with por.

This is why Spanish does not say it the way English often does, such as mop the floor or wipe the table. Spanish is thinking more like:

• pass the mop over the floor
• pass the cloth over the table

In Spain, la bayeta usually means a cleaning cloth or dishcloth, the kind you use to wipe surfaces.

So:

• la bayeta = cleaning cloth
• el trapo = cloth/rag
• el paño = cloth, often a bit more neutral or general

Bayeta is very common in Spain specifically. A learner used to Latin American Spanish may hear other words more often depending on the country.

Because Spanish often omits repeated words when the meaning is clear.

The full version would be:

• Cuando terminemos de comer, pasaremos la mopa por el suelo y luego pasaremos la bayeta por la mesa de la cocina.

But once pasaremos has already been said, Spanish can leave it out in the second part:

• ...pasaremos la mopa por el suelo y luego la bayeta por la mesa...

This is a normal kind of ellipsis. English does something similar sometimes:

• We’ll mop the floor and then the table with a cloth.

Because with pasar in this cleaning sense, por is the usual preposition. It expresses movement over a surface.

• pasar la mopa por el suelo
• pasar la bayeta por la mesa
• pasar la mano por la pared

Using por here is the standard choice.

• sobre would sound more like above/on top of and is not the normal preposition in this expression.
• en does not work well with this verb pattern in this meaning.

So this is something best learned as a chunk:

• pasar algo por + surface

Because Spanish uses definite articles much more often than English, especially with everyday objects and parts of a known situation.

Here the sentence refers to specific, understood things:

• la mopa = the mop
• el suelo = the floor
• la bayeta = the cloth
• la mesa de la cocina = the kitchen table

Even when English might prefer no article in a more general verb phrase like mop the floor or wipe the table, Spanish naturally keeps the article.

In this sentence, el suelo means the floor as a surface inside a room.

In Spain:

• suelo = floor, ground, surface under your feet
• piso can also mean floor, but very often it means flat/apartment

Because piso has that very common meaning of apartment in Spain, suelo is often the clearest and most natural choice for the literal floor surface in a sentence like this.

It can mean both, depending on context.

In your sentence, luego means then / after that:

• ...y luego la bayeta por la mesa... = ...and then the cloth over the kitchen table...

It links the next step in a sequence.

Other possible words here could be:

• después
• después de eso

But luego is very natural.

In natural English, you would usually translate la mesa de la cocina as the kitchen table.

Literally, it is the table of the kitchen, but that is not how English normally says it. The phrase de la cocina tells you which table it is: the one belonging to / associated with the kitchen.

So:

• la mesa de la cocina = the kitchen table

Here de la cocina modifies la mesa, not the whole sentence.

Yes. Acabar de comer and terminar de comer can both mean to finish eating.

So this would also be natural:

• Cuando acabemos de comer, pasaremos la mopa...

In many contexts, acabar and terminar are very close in meaning. Which one is chosen often depends on personal preference or region.

Just be careful with acabar de + infinitive, because it can also mean to have just done something in other contexts:

• Acabo de comer = I’ve just eaten

But in cuando acabemos de comer, the meaning is clearly when we finish eating.

Yes, and it would be very similar in meaning:

• Después de comer, pasaremos la mopa...

That means After eating, we’ll mop...

The difference is small:

• cuando terminemos de comer focuses on the moment when we finish
• después de comer simply means after eating

Both are natural. The original version sounds a little more precise about sequence.

Yes, it sounds very much like Spain Spanish, especially because of words like bayeta and the household phrasing.

A few things that make it feel Spain-oriented:

• la bayeta is very common in Spain
• pasar la mopa is also very typical household vocabulary in Spain
• the overall sentence sounds like everyday domestic Spanish from Spain

A speaker from another Spanish-speaking country would understand it, but they might choose slightly different words.