Stasera esco in compagnia e porto con me il mio portachiavi, che ha una piccola luce incorporata.

Stasera means this evening or tonight.

Yes, you can also say questa sera. They mean essentially the same thing:

• Stasera esco = I’m going out tonight
• Questa sera esco = same meaning

Stasera is very common in everyday speech and feels a bit more compact and conversational.

Italian often uses the present tense to talk about the near future when the time is already clear.

So:

• Stasera esco = literally Tonight I go out, but naturally I’m going out tonight

This works because stasera already tells you the action is in the future.
You could also say stasera uscirò, using the future tense, but stasera esco sounds very natural in everyday Italian.

Italian usually drops subject pronouns when they are not needed, because the verb ending already shows who is doing the action.

• esco = I go out
• porto = I bring / I carry

The -o ending tells you the subject is I.

You would add io only for emphasis or contrast:

• Io esco, ma lui resta a casa = I’m going out, but he’s staying home

In compagnia is an idiomatic expression meaning in company, with other people, or more naturally in English, not alone.

So esco in compagnia means something like:

• I’m going out with others
• I’m going out in company
• I’m going out with friends / with people

It does not necessarily specify who the people are. If you want to be specific, you could say:

• esco con gli amici = I’m going out with friends
• esco con la mia ragazza = I’m going out with my girlfriend

Because in compagnia is a fixed Italian expression.

Italian often uses certain prepositions in ways that do not match English word-for-word. Here, the natural idiom is:

• essere in compagnia
• uscire in compagnia

Using con compagnia would sound unnatural.
Using nella compagnia would mean something much more literal, like inside the company/group, which is not the idea here.

Porto by itself already means I bring or I carry.
Adding con me makes the idea more explicit: I’m taking it with me.

So:

• porto il mio portachiavi = I bring my keychain
• porto con me il mio portachiavi = I bring my keychain with me

The version with con me is very common and natural, especially when you want to stress that the object accompanies you.

Portachiavi means keychain or keyring.

It is a compound noun, and even though it ends in -i, it can still be singular:

• il portachiavi = the keychain
• i portachiavi = the keychains

So the word is usually invariable in the plural: the form stays the same, and the article tells you whether it is singular or plural.

This is a good reminder that in Italian, an -i ending does not always mean a word is plural.

In Italian, possessives usually take the definite article:

• il mio libro
• la mia macchina
• il mio portachiavi

So il mio portachiavi is the normal form.

The main common exception is with many singular family members:

• mio fratello
• mia madre
• mio padre

But portachiavi is not in that group, so it needs the article.

The comma shows that che ha una piccola luce incorporata is extra information about the keychain, not information needed to identify it.

So the sentence means:

• my keychain, which has a small built-in light

This is a non-restrictive relative clause.

Without the comma, the meaning would lean more toward:

• the keychain that has a small built-in light as if you were distinguishing it from other keychains.

In this sentence, the speaker already means a specific keychain: il mio portachiavi. The clause just adds a detail about it.

Here che is correct because it is the subject of the relative clause:

• il mio portachiavi, che ha una piccola luce incorporata
• literally: my keychain, which has a small built-in light

In the relative clause, che = which, and it is the thing doing the verb ha.

Cui is usually used:

• after a preposition: il portachiavi di cui parlo = the keychain that I’m talking about
• in more specific relative structures

So in this sentence, che is the simple and correct choice.

Because the idea is that the keychain has a feature: a small built-in light.

So:

• ha = has
• una piccola luce incorporata = a small built-in light

This is a very natural way to describe an object and one of its features in Italian.

You could think of it as:

• a keychain that has a built-in light

If you changed the structure, the meaning would shift. For example:

• il portachiavi è incorporato would mean the keychain is built in, which is a different idea

Here the thing that is incorporated is the light, not the keychain.

Because incorporata agrees with luce, and luce is a feminine singular noun.

So:

• una luce incorporata
• piccola also agrees with luce

That gives you:

• una piccola luce incorporata

It does not agree with portachiavi, because incorporata is describing the light, not the keychain.

If it described portachiavi, it would have to be masculine:

• un portachiavi incorporato

But that is not what the sentence means.

Italian adjective position is more flexible than English, but some patterns are very common.

In una piccola luce incorporata:

• piccola comes before the noun very naturally, because common descriptive adjectives like piccolo, grande, bello, brutto often appear before the noun
• incorporata comes after the noun because it is more classifying or technical: it tells you what kind of light it is

So the phrase sounds natural and idiomatic.

You may also see other possibilities in Italian, but this order is perfectly normal:

• una piccola luce incorporata = a small built-in light