Cylinders, cones, and spheres are all round solids, but they differ in how many bases they have and what shape those bases are.
Cylinders, cones, and spheres all have a round part, but counting their bases tells them apart for sure. A cylinder has 2 circular bases of the same size, top and bottom, wrapped by a curved side face. Cans and rolls of paper towels are classic cylinder shapes.
A cone has only 1 base, with its side face coming to a single pointed apex — just picture a party hat. A sphere has 0 flat faces at all — it's a perfectly round shape where the distance from the center to the surface is always the same, no matter the direction.
Click the net button and the differences become even clearer. A cylinder's side face unfolds into a rectangle, and a cone's side face unfolds into a sector (a pie-slice shape) — but no matter how you cut a sphere, it can never be flattened out.