Learn Spanish (Latin America): Tú compras un carro, pero yo necesito una bicicleta.

In Spanish, words for a or an (indefinite articles) have to match the gender of the noun they describe. Carro is a masculine noun, so it takes the masculine article un. Bicicleta is a feminine noun, so it takes the feminine article una.

I thought we could drop words like tú and yo. Why are they included here?

You are right! Usually, the verb endings (compras, necesito) already tell us who is doing the action. However, Spanish speakers often include pronouns like tú and yo when they want to show a strong contrast between two people, similar to emphasizing you do this, but I do that in English.

Why does Tú have an accent mark?

The accent mark changes the meaning of the word. Tú with the accent means you (as the subject of a sentence, like here). Tu without the accent means your (as in tu carro, meaning your car). The accent simply helps tell these two identical-sounding words apart in writing.

Is carro the only Spanish word for car?