Το γκαζάκι είναι δίπλα στην ψησταριά και λειτουργεί καλά.

Το is the definite article meaning the.

So το γκαζάκι = the little gas stove / the camping stove.

Greek articles change depending on gender, number, and case. Here:

• το = the for a neuter singular noun
• γκαζάκι is a neuter singular noun

So the subject of the sentence is το γκαζάκι.

Γκαζάκι usually means a small gas burner, portable gas stove, or camping stove.

The ending -άκι is very often a diminutive ending in Greek. It can suggest something small, and sometimes also something more familiar or informal.

So compared with γκάζι or other gas-related words, γκαζάκι often gives the idea of a small gas appliance.

Yes. Είναι means is (or are, depending on context).

In this sentence:

• Το γκαζάκι είναι... = The gas stove is...

A useful thing to know is that είναι is the same form for:

• he/she/it is
• they are
• and it is also used with you are in the polite form

Here it clearly means it is, because the subject is το γκαζάκι.

Δίπλα means next to or beside.

Very often, δίπλα is followed by σε + a noun:

• δίπλα σε κάτι = next to something

In your sentence, that structure appears in a contracted form:

• δίπλα στην ψησταριά

which comes from:

• δίπλα σε την ψησταριά

In modern Greek, σε + την normally becomes στην.

So the whole phrase means:

• next to the grill

Because in modern Greek, σε often combines with the definite article.

Common contractions are:

• σε + τον = στον
• σε + τη / την = στη / στην
• σε + το = στο

So:

• σε την ψησταριά becomes στην ψησταριά

Both help express in / at / on / to, depending on context.
Here, after δίπλα, it gives the meaning next to the grill.

Yes. After σε (and therefore after στη / στην / στο / στον), the noun normally appears in the accusative.

So:

• nominative: η ψησταριά = the grill
• accusative: την ψησταριά

That is why the sentence has:

• στην ψησταριά

For this noun, the article changes clearly:

• η → την

The noun itself, ψησταριά, happens to look the same in nominative and accusative singular.

Ψησταριά means grill, barbecue grill, or grill rack, depending on context.

It comes from the idea of roasting/grilling. In everyday use, it often refers to the device or place where food is grilled.

So in this sentence:

• δίπλα στην ψησταριά = next to the grill

The final -ν in forms like στην is kept before certain sounds, and in standard modern Greek it is very normal before a word beginning with a consonant such as ψ.

Since the next word is:

• ψησταριά

you get:

• στην ψησταριά

You will also often see:

• στη ψησταριά

in some contexts or less careful writing/speech, but στην ψησταριά is fully standard and very natural.

Και means and.

It connects the two parts of the sentence:

• Το γκαζάκι είναι δίπλα στην ψησταριά
• και λειτουργεί καλά

So the sentence gives two pieces of information about the same subject:

1. where it is
2. how it is functioning

Λειτουργεί means works, functions, or operates.

Here it refers to the gas stove functioning properly:

• λειτουργεί καλά = it works well

This is the 3rd person singular form, matching το γκαζάκι.

You can think of it as:

• I work/function = λειτουργώ
• it works/functions = λειτουργεί

Because καλά here is an adverb, meaning well.

It modifies the verb λειτουργεί:

• λειτουργεί καλά = works well

Compare:

• καλός / καλή / καλό = good (adjective, describes a noun)
• καλά = well (adverb, describes a verb)

So:

• ένα καλό γκαζάκι = a good stove
• το γκαζάκι λειτουργεί καλά = the stove works well

It is fairly close to English here:

• Το γκαζάκι = subject
• είναι δίπλα στην ψησταριά = first statement
• και λειτουργεί καλά = second statement

So literally:

• The gas stove is next to the grill and works well.

Greek word order is often more flexible than English, but this sentence uses a very natural, straightforward order.

No. Greek often leaves out subject pronouns, and here the subject noun has already been stated:

• Το γκαζάκι είναι δίπλα στην ψησταριά και λειτουργεί καλά.

It is understood that λειτουργεί still refers to το γκαζάκι.

In English, we would usually repeat it:

• The gas stove is next to the grill and it works well.

But Greek does not need that extra pronoun here.