how to remove black background from a picture?

[#1]

so this is a very beginner problem, but i have no idea how to remove a black background from a regular image, but this could apply to any color. ive seen people do it before doing something much simpler than i do, but i could never figure out what. for now i am doing a very slow and time consuming process of using clipping masks. ive tried everyting. thanks!

[#2]

so this is a very beginner problem, but i have no idea how to remove a black background from a regular image, but this could apply to any color. ive seen people do it before doing something much simpler than i do, but i could never figure out what. for now i am doing a very slow and time consuming process of using clipping masks. ive tried everyting. thanks!

[#3]

Illustrator is not the correct tool for image editing. For that you'd best use Photoshop.