El hervidor está en la cocina, al lado de la cafetera.

Because Spanish uses estar for location.

When you say where a person or thing is, you normally use estar:

• El hervidor está en la cocina.
• La cafetera está en la encimera.

Use ser for identity, classification, or essential description:

• Es un hervidor.
• La cocina es pequeña.

So here, since the sentence tells us where the kettle is, está is the correct choice.

Because Spanish nouns have grammatical gender, and the article has to match the noun:

• el hervidor = masculine
• la cocina = feminine
• la cafetera = feminine

You usually have to learn the gender along with the noun. There are patterns, but they are not perfect rules:

• nouns ending in -dor are often masculine: el hervidor
• nouns ending in -a are often feminine: la cocina, la cafetera

The article is not optional here; Spanish normally uses it with specific objects and places.

In Spanish, you normally use the definite article with rooms and familiar places when you mean a specific one:

• en la cocina
• en el baño
• en el salón

So está en la cocina sounds natural, while está en cocina would sound wrong in standard Spanish.

English often drops the in places where Spanish keeps the article.

Hervidor means a kettle or a device used to boil water.

In Spain, hervidor is understandable, and hervidor de agua is even more explicit if you want to be very clear.

A useful distinction:

• hervidor / hervidor de agua = kettle, water boiler
• tetera = teapot

So if you mean the appliance for boiling water, hervidor is a good choice.

Here, cafetera means coffee maker or coffee pot, depending on context. In this sentence, coffee maker is the most natural interpretation.

It is not the same as English cafeteria.

Some related words:

• cafetera = coffee maker / coffeepot
• cafetería = café, coffee shop, cafeteria

Notice the accent and the ending: cafetera and cafetería are different words.

Al lado de means next to, beside, or by the side of.

Examples:

• El hervidor está al lado de la cafetera.
• La mesa está al lado de la ventana.

It is a very common way to describe position.

Because al is the contraction of a + el.

This expression is historically:

• a + el lado de → al lado de

So al lado de is the fixed form you learn and use.

A helpful way to think of it is that it literally comes from something like at the side of.

Because al lado de is a complete expression, and de introduces the thing something is next to.

So:

• al lado de la cafetera = next to the coffee maker
• al lado del microondas = next to the microwave

Notice this pattern:

• de + el = del
• de + la = de la

That is why we get:

• al lado del horno
• al lado de la cafetera

The accent mark shows the correct stress and also distinguishes it from esta.

• está = a form of estar
• esta = this (feminine), as in esta cocina

So in the sentence, está is clearly the verb.

Not really. The sentence works with or without the comma.

• El hervidor está en la cocina, al lado de la cafetera.
• El hervidor está en la cocina al lado de la cafetera.

With the comma, the second part can sound a little more like an added clarification. Without the comma, it feels slightly more tightly connected. In everyday writing, many native speakers would simply leave the comma out.

Yes, but the original order is the most neutral and natural:

• El hervidor está en la cocina, al lado de la cafetera.

Spanish word order is flexible, but changes often add emphasis:

• En la cocina, al lado de la cafetera, está el hervidor.
  This sounds more emphatic or descriptive.

For a learner, the original version is the safest and most natural choice.

A simple pronunciation guide for Spain Spanish would be roughly:

el er-bi-DOR es-TA en la ko-THEE-na, al LA-do de la ka-fe-TE-ra

A few useful notes:

• h in hervidor is silent
• in most of Spain, c before i in cocina sounds like the th in thin
• the stress falls on:
  • herviDOR
  • esTÁ
  • coCIna
  • cafeTEra

So cocina in Spain is roughly ko-THEE-na.