The are two types of Mice available for using on a PC. There are mice with a ball in them and optical mice.
The traditional mouse was the mouse with a ball in it. The ball turns rollers in the mouse when it is moved and sends those movements to the computer which moves the pointer on the screen based on that. You have to use the ball mouse on a flat surface and usually in a horizontal mode to get it to work correctly.
In recent years the optical mouse was introduced and now is the mouse you see in the stores and is most popular. This mouse has a laser in it that detects when you move the mouse. there are no moving parts in the optical mousse. The red light you se on the mouse is the laser. It is a low powered laser but you still need to treat correctly and do not point the light from it at people's faces.
The optical mouse is not limited to using on horizontal flat surfaces but can be used anywhere the laser picks up the motion. I have used mine on my legs when using a laptop. I have watched people use them on walls.
The ball mouse will build dirt in it that can be cleaned. If the mouse starts being bumpy when you move it, it needs cleaning. Turn the mouse over and there is a cover over the ball, You can turn that cover and it will come off. Then lift the ball out (basically looks like a small superball) and then look at the rollers. They should be clean and not have a band on them. the band that is there is dirt and you can take a flat object and scrape the dirt off. I use my finger nail. Turn the roller as you do that. Put the roller back in and put the cover back on and twist opposite the arrow and it will tighten down, It will feel like a new mouse.
The optical mouse usually only needs the pads on bottom wiped off occasionally to have it glide more smoothly.