Zatímco se v pračce pere prádlo, moje sestra suší ponožky a žehlí košile.

Zatímco means while or whereas, depending on context.

In this sentence, it means while, because it connects two actions happening at the same time:

• Zatímco se v pračce pere prádlo = While the laundry is being washed in the washing machine
• moje sestra suší ponožky a žehlí košile = my sister is drying socks and ironing shirts

So here it introduces a time relationship, not a contrast.

Here se helps create an impersonal or passive-like meaning.

The verb prát means to wash.
But prát se in this kind of structure can mean something like:

• the laundry is being washed
• washing is happening

So se v pračce pere prádlo is not saying that the laundry is washing itself literally. It is a very natural Czech way to express that the washing is going on, without focusing on who is doing it.

A very close English equivalent would be:

• The laundry is being washed in the washing machine

Pere prádlo uses a normal present-tense verb with se, which is a common, natural Czech way to describe an ongoing process.

So:

• pere se prádlo / se pere prádlo = the laundry is being washed
• je prané would mean something more like it is washed or it is in a washed state

The sentence wants to describe an action in progress, so pere se is the better choice.

Yes, Czech word order is flexible.

This sentence uses a natural order, but other versions are possible, for example:

• Zatímco se v pračce pere prádlo...
• Zatímco se prádlo pere v pračce...
• Zatímco prádlo se pere v pračce... (less neutral in many contexts)

The chosen order sounds smooth and natural. Czech often places short words like se early in the clause, usually in second position or near the beginning of the clause.

So one important thing to notice is:

• se tends to come very early
• word order often reflects emphasis more than strict grammar roles

V pračce is in the locative case because it follows the preposition v meaning in.

The dictionary form is:

• pračka = washing machine

After v, it becomes:

• v pračce = in the washing machine

So this is a normal case change:

• nominative: pračka
• locative: v pračce

Many feminine nouns change like this after v.

Prádlo is a neuter noun and is grammatically singular, but its meaning is often collective.

It usually means:

• laundry
• washing
• sometimes linen or clothes to be washed

So although English often thinks of laundry as an uncountable noun, Czech uses prádlo as a singular noun:

• To prádlo je mokré. = The laundry is wet.

In your sentence, prádlo is the thing being washed.

They are in the accusative plural, because they are the direct objects of the verbs:

• suší ponožky = she dries socks
• žehlí košile = she irons shirts

Dictionary forms:

• ponožka = sock
• košile = shirt

Plural forms here:

• ponožky
• košile

For these nouns, the accusative plural looks the same as the nominative plural, so the forms do not change visibly here.

In Czech present tense, the 3rd person singular form is used for:

• he
• she
• it

So:

• suší = he/she/it dries
• žehlí = he/she/it irons

Because the subject is moje sestra (my sister), English translates them as she dries and she irons.

Czech does not need a separate verb ending just for she.

Because Czech normally uses the simple present tense where English often uses the present continuous.

So Czech says:

• moje sestra suší ponožky a žehlí košile

Literally this is closer to:

• my sister dries socks and irons shirts

But in context, English naturally translates it as:

• my sister is drying socks and ironing shirts

This is very common in Czech. Present tense can describe actions happening right now.

The comma separates the subordinate clause from the main clause.

The first clause begins with Zatímco:

• Zatímco se v pračce pere prádlo

Then the main clause follows:

• moje sestra suší ponožky a žehlí košile

Czech punctuation regularly uses a comma to separate clauses like this, especially when a sentence begins with a conjunction such as zatímco.

Yes. A simply means and.

It connects the two actions done by the sister:

• suší ponožky
• a žehlí košile

So:

• moje sestra suší ponožky a žehlí košile
• my sister is drying socks and ironing shirts

These verbs are imperfective:

• prát = to wash
• sušit = to dry
• žehlit = to iron

Imperfective verbs are used for:

• ongoing actions
• repeated actions
• general processes

That is exactly what the sentence describes: actions in progress.

So the present tense here naturally means:

• laundry is being washed
• sister is drying socks
• sister is ironing shirts

If perfective verbs were used, the meaning would change and would usually not fit this ongoing scene.

Grammatically you could build a sentence like that in English, but it sounds less natural than the intended meaning.

The Czech sentence focuses on the process, not on the machine as an active subject. So the best translation is something like:

• While the laundry is being washed in the washing machine...
• While the laundry is washing in the machine... (less formal, but possible in English)

So v pračce means in the washing machine, but the machine is not really the grammatical subject in Czech here.

Because Czech has no articles.

So nouns like:

• prádlo
• ponožky
• košile
• sestra

do not automatically need words like a or the.

Whether something is understood as definite or indefinite depends on context.

For example:

• moje sestra clearly means my sister
• prádlo here naturally means the laundry
• ponožky and košile are understood from context as socks and shirts

English must choose articles, but Czech does not.