Learn Italian: È lui.

Italian doesn't use a filler word for 'it' like English does in sentences like 'It is him' or 'It is raining'. The verb È (is) can stand on its own. This is part of the pro-drop rule where Italian drops the subject pronoun because the verb already makes the meaning clear.

Does lui mean 'he' or 'him'?

It translates to both depending on the sentence! You are learning lui as the subject pronoun 'he'. However, just like we say 'It is him' in conversational English, Italian uses lui to identify a male person after the verb to be.

Why does È have an accent mark?

The accent mark is essential for meaning. È with the accent means 'is'. If you write it without the accent, e means 'and'.

Could I say Lui è to mean the same thing?

Not exactly. Lui è translates to 'He is...' and usually needs more information to finish the sentence, like Lui è un uomo (He is a man). When you are identifying someone by saying 'It is him', the verb comes first: È lui.