to play (a stringed or keyboard instrument)
「弾く」 has another reading with different meanings.
to flip; to snap; to flick
to pull; to tug; to lead (e.g. a horse)
to flick out; to spring out; to repel
毎晩ピアノを弾いている。
I play the piano every night.
姉がギターを弾くのが上手だ。
My older sister is good at playing guitar.
子供の頃からバイオリンを弾いていた。
I've been playing violin since childhood.