A recessed fixture is really two parts. First, there is the electrical part, called inexplicably a "can". The decorative part is called a trim...
But there many kinds of trims for different applications.
Multi use....Definitely the most popular is called the baffle...Just a white cone for your white ceiling.
Directional....Shining specific areas like walls or different objects. Look at eyeballs, gimbals, pinholes and half moons depending on the application.
Shower....Wet location or covered trims.