Learn Italian: È un gatto.

Because gatto (cat) is a masculine word. In Italian, most masculine words that start with a regular consonant take un for "a" or "an". If the word were feminine, like mela (apple), you would use una.

Where is the word for "it" in this sentence?

Italian usually drops subject words like "it", "he", or "she" because the verb already shows who or what is doing the action. The single word È means "it is" all by itself!

Why does È have an accent mark?

The accent mark is very important because it helps tell apart two completely different words. È with the accent means "is", while e without the accent means "and".

Can un gatto refer to a female cat?

Usually, gatto refers to a male cat or a cat in general. Words ending in -o are generally masculine. If you want to specify that a cat is female, you change the ending to -a and use the feminine article, making it una gatta.