Learn Italian: Anna è andata in biblioteca ieri. - Anna went to the library yesterday.

In Italian, the past tense (passato prossimo) usually uses the auxiliary (helper) verb avere (to have). However, verbs that describe movement from one place to another, like andare (to go), use essere (to be) instead. So, this sentence literally works like Anna is gone rather than Anna has gone.

Why does the verb andata end in -a?

When you form the past tense with the auxiliary verb essere, the past participle (the main action word, here andata) must match the gender and number of the subject. Because Anna is female (feminine singular), the default ending -o changes to -a. If the subject were male, it would be è andato.

Why do we say in biblioteca for to the library instead of using the preposition a?

The preposition in is used without a definite article (like the word the) for specific types of places. This includes countries, certain rooms, and words ending in -teca like biblioteca (library). After a movement verb like andare, in simply translates to to the.

Does ieri have to go at the end of the sentence?

Not necessarily! Time words like ieri (yesterday) are flexible. You can put it at the very beginning of the sentence to strongly emphasize when she went, but putting it at the end is the standard, neutral choice.