Learn Romanian: Îi dau cartea lui Andrei. - I give the book to Andrei.

In Romanian, it is standard to double the indirect object using a short pronoun. Îi literally means 'to him', so the sentence translates word-for-word as 'To him I give the book to Andrei.' This feels redundant in English, but it is a normal and often required rule in Romanian grammar to point out who receives an action.

Does the word lui mean 'his' in this sentence?

Not exactly. While lui is often used for possession (like in 'cartea lui' for 'his book'), here it is used to show the receiver of the action. This is called the Dative case. When giving something to a specific male person by name, you place lui right before the name to mean 'to [Name]'. So lui Andrei means 'to Andrei'.

Where is the word for 'I' in this sentence?

It is built right into the verb. Dau is the first-person singular present form of the verb a da (to give). Because the spelling of dau already tells us that 'I' am doing the action, the pronoun eu (I) is usually dropped unless you really want to emphasize it.

Why is the word for book spelled cartea instead of just carte?

Because the sentence is about 'the' book, not just 'a' book. In Romanian, the word for 'the' (the definite article) attaches to the very end of the noun. For feminine words ending in -e like carte, adding the article turns the ending into -ea, giving us cartea (the book).