En esa empresa trabajan doscientas personas.

Because en esa empresa means in that company or at that company, and it sets the location first.

Spanish often puts the place or context at the beginning if that is the starting point of the sentence. So:

• En esa empresa trabajan doscientas personas. = At that company, two hundred people work.
• More natural English meaning: Two hundred people work at that company.

This word order is very normal in Spanish.

Because empresa is a feminine singular noun, so the demonstrative has to agree with it.

The feminine singular form is:

• esta = this
• esa = that
• aquella = that over there / that one farther away

So:

• esa empresa = that company

You cannot say ese empresa because ese is masculine.

Because it takes feminine words with it:

• la empresa
• esa empresa
• una empresa

Many Spanish nouns ending in -a are feminine, and empresa is one of them.

That matters because other words must match it in gender where needed.

Because the subject is doscientas personas, which is plural.

Even though the subject comes after the verb, it is still the subject. So the verb must agree with two hundred people, not with empresa.

• trabaja = he/she/it works
• trabajan = they work

So:

• En esa empresa trabajan doscientas personas.
• Literally: In that company work two hundred people.

Spanish allows much freer word order than English.

Both of these are correct:

• En esa empresa trabajan doscientas personas.
• Doscientas personas trabajan en esa empresa.

The version with trabajan before doscientas personas is very natural, especially when the sentence begins with a place expression like en esa empresa.

English usually prefers subject + verb, but Spanish does not always have to.

Because doscientos/doscientas agrees in gender with the noun it modifies, and personas is feminine.

So:

• doscientos hombres = two hundred men
• doscientas personas = two hundred people

This is an important feature of the hundreds in Spanish:

• doscientos / doscientas
• trescientos / trescientas
• cuatrocientos / cuatrocientas, etc.

Because persona is always a feminine grammatical noun, regardless of the actual sex of the person being referred to.

So even if the group is mixed, you still say:

• doscientas personas

This is grammatical gender, not biological gender.

Usually, no—not unless the context already makes it very clear what doscientas refers to.

On its own, doscientas sounds incomplete because the listener expects a feminine plural noun after it:

• doscientas personas
• doscientas empleadas
• doscientas horas, etc.

So in this sentence, personas is normally needed.

Yes, but it is not exactly the same.

• Hay doscientas personas en esa empresa = There are two hundred people in that company
• En esa empresa trabajan doscientas personas = Two hundred people work at that company

The first one focuses more on existence or number. The second one clearly says those people work there.

So they are similar, but not identical.

It can correspond to either in or at in English, depending on what sounds natural.

With empresa, English usually says:

• at that company
• or in that company

Both are understandable, but at that company is often the more natural English translation.

In Spanish, en covers both ideas here.

No, not in this meaning.

If you want to say that two hundred people work at/in that company, you need en:

• En esa empresa trabajan doscientas personas.

Without en, esa empresa would no longer function as the place expression, and the sentence would sound wrong.

Not necessarily. In this sentence, trabajan is in the present tense, but it often expresses a general fact, not just what is happening at this exact moment.

So here it means something like:

• Two hundred people work at that company
• That company employs two hundred people

It describes a normal situation or fact.

A simple Spain pronunciation guide:

• doscientas ≈ dohs-SYEN-tahs
• personas ≈ pehr-SO-nahs

A few helpful notes:

• The stress in doscientas is on cien.
• The stress in personas is on so.
• In much of Spain, the c before i in doscientas is pronounced like the th in think:
  • dohs-THYEN-tahs
• In Latin America, it is usually pronounced with an s sound instead.

Not exactly from the Spanish alone.

The sentence says doscientas personas = two hundred people. That is broader than employees.

In many real situations, the intended meaning may indeed be employees, but the Spanish word used here is still personas, not empleados or trabajadores.

So the safest translation is two hundred people unless context tells you otherwise.