Learn Russian: Музыкант играет.

Russian doesn't have articles like "the" or "a". The word музыкант can mean "a musician", "the musician", or just "musician" depending on the context.

The translation says "is playing", but could this also mean "The musician plays"?

Yes! Russian has only one present tense. So, Музыкант играет translates to both "The musician is playing" (right now) and "The musician plays" (in general, like a habit).

Why does the verb играет end in -ет?

It is the "he/she/it" ending for the verb играть (to play). Because музыкант (musician) is a "he" or "she" (third-person singular), we drop the -ть from the dictionary form and add -ет.

The word музыкант looks and sounds like the English word "musician". Is that common?

Very common! Russian has many "cognates"—words that sound similar to English and mean the same thing. You will often see this with professions, arts, and modern technology.