a sphere is a plane folded in on itself, and spheres have no (one-dimensional) holes. but spheres do have a two-dimensional hole, which is basically a way of saying they’re hollow.

a circle is a line folded in on itself, and circles have one (one-dimensional) hole.

edit: the claim that circles and straws are homotopic is basically a fancy way of saying: “if you place a straw upright on a table and flatten it by smashing your hand down on it, you will end up with a circle.”