The art that an artist has done is called his or her "work". You might have heard the word "artwork". And maybe you've heard the phrase "a work of art":
The Louvre in Paris has over 35,000 works of art.
"Works" of art mean pieces or items of art. You can count them like in the example above. But when you're talking about the art that a particular artist has done, you call it their "work" (singular):
His work isn't that innovative.
Even some of her earlier work was really ingenious.
"Work" can refer to any kind of art form: music, acting, paintings, novels, and many others.