Learn Romanian: Fata poartă o fustă roșie. - The girl is wearing a red skirt.

In Romanian, the word for "the" (the definite article) attaches to the end of the noun. The basic word for "girl" is fată, and to say "the girl", you change the ending to get fata.

Does poartă mean "wears" or "is wearing"?

It can mean both! Romanian doesn't have a separate tense for actions happening right now. You just use the simple present tense verb poartă for both "wears" and "is wearing".

Why does the color come after the skirt (fustă roșie)?

In Romanian, descriptive words (adjectives) usually come right after the noun they describe. So instead of "red skirt", you literally say "skirt red" (fustă roșie).

I've seen the word for red as roșu. Why is it roșie here?

Adjectives change their endings to match the gender of the noun. Because fustă (skirt) is a feminine noun, the adjective takes its feminine singular form, roșie. If it were a masculine noun, you would use roșu.