Cuando llegamos a la terminal, había mucha gente en la puerta de embarque.

Because llegamos is in the preterite, which presents the arrival as a completed event: we arrived, and then the next situation is described.

• Cuando llegamos... = When we arrived...
• Cuando llegábamos... would mean something more like When we were arriving... or As we were arriving..., which gives a more in-progress feeling.

In this sentence, the arrival is treated as the point in time at which the speaker notices the crowd, so preterite is the natural choice.

Había is the imperfect form of haber used to mean there was / there were. It is used here to describe the background situation at that moment.

• había mucha gente = there were a lot of people
• It paints the scene rather than highlighting a single completed event.

Compare:

• Cuando llegamos, había mucha gente...
  = When we arrived, there were lots of people...
• Cuando llegamos, hubo mucha gente...
  sounds much less natural here, because hubo usually refers to the fact that something occurred or came about, not simply the background situation you found on arrival.

So the contrast is very common in Spanish:

• preterite for the main event: llegamos
• imperfect for the surrounding description: había

Because when haber means there is / there are / there was / there were, it is impersonal in standard Spanish. That means it stays in the singular.

So:

• hay mucha gente
• había mucha gente
• hubo muchas personas

Even if what follows is plural in meaning, the verb does not agree with it.

Standard Spanish says:

• Había muchas personas ✅ not
• Habían muchas personas ❌

This is a very common learner question because English uses were with plurals, but Spanish does not do that with impersonal haber.

Because gente is normally a singular feminine noun meaning people in a collective sense.

So it takes:

• mucha gente ✅

Not:

• muchos gente ❌ because gente is feminine
• muchas gentes ❌ in this context, because gente is usually treated as an uncountable collective noun

Even though it refers to many people, grammatically it is singular:

• La gente está esperando.
• Había mucha gente.

You can use personas if you want a normal plural noun:

• Había muchas personas.

In Spanish, it is very common to use the definite article where English might use the, a, or sometimes nothing depending on context. Here la terminal means the terminal, referring to the relevant terminal in the situation.

Spanish generally likes articles with nouns more than English does. Since the speaker and listener can identify the place being talked about, la terminal sounds natural.

Also, terminal is a feminine noun in this meaning:

• la terminal
• una terminal

Because en is used to indicate location: the people were at / in the boarding gate area.

• en la puerta de embarque = at the boarding gate

If you used a, it would usually suggest movement toward something:

• fuimos a la puerta de embarque = we went to the boarding gate

Here there is no movement in that phrase; it is describing where the crowd was, so en is the right preposition.

Literally, puerta de embarque is something like boarding gate.

It is a very common Spanish structure:

• noun + de + noun

Here:

• puerta = gate / door
• de embarque = of boarding

So puerta de embarque means the gate associated with boarding.

Spanish often uses de where English uses a noun directly as an adjective:

• tarjeta de crédito = credit card
• sala de espera = waiting room
• puerta de embarque = boarding gate

Yes, llegamos can be either:

• present: we arrive
• preterite: we arrived

The context tells you which one it is.

In this sentence, Cuando llegamos a la terminal, había... clearly points to the preterite, because it is narrating a past situation.

This kind of form overlap is very common in Spanish verbs:

• hablamos
• comemos is not ambiguous in the same way, but many -ar verbs are

Context usually makes it completely clear.

The comma separates the time clause from the main clause:

• Cuando llegamos a la terminal, = time/background clause
• había mucha gente en la puerta de embarque. = main clause

In English, you also often use a comma after an introductory clause:

• When we arrived at the terminal, there were lots of people at the boarding gate.

In Spanish, this punctuation is normal and helps readability.

No, not in standard Spanish for this meaning.

Use:

• haber to express existence: there is / there are / there was / there were
• estar to express location or state of something already identified

So:

• Había mucha gente en la puerta de embarque. ✅
  = There were lots of people at the boarding gate.

But:

• La gente estaba en la puerta de embarque. ✅
  = The people were at the boarding gate.

The difference is:

• había introduces the existence of the people
• estaba/estaban talks about where specific people were

Yes. You could say:

• Cuando llegamos a la terminal, había muchas personas en la puerta de embarque.

That is grammatically correct. However, mucha gente is often more natural and idiomatic in everyday Spanish when you just mean a lot of people in a general sense.

The difference is roughly:

• mucha gente = lots of people, more collective and common
• muchas personas = many people, a bit more explicit or slightly more formal depending on context

Because the sentence refers to a real past event.

• Cuando llegamos... = when we arrived

Spanish uses the indicative after cuando when the event is seen as real, habitual, or already known.

You get the subjunctive after cuando when referring to the future or something not yet realized:

• Cuando lleguemos a la terminal, te llamo.
  = When we arrive at the terminal, I’ll call you.

So:

• cuando llegamos = real past event → indicative
• cuando lleguemos = future event → subjunctive

Because that is one of the most important patterns in Spanish narration.

The sentence uses:

• llegamos = preterite for the completed action
• había = imperfect for the background scene

This combination is extremely common:

• Llegué y hacía frío.
• Entraron y había música.
• Cuando salimos, llovía.

A useful way to think about it is:

• preterite = what happened
• imperfect = what was going on / what the situation was like

So the sentence is a classic example of Spanish storytelling structure.