When you jump, you lift both legs off the ground at the same time.
When you hop, you lift either leg off the ground but not both.
"Both" is similar to "all"
e.g. Which film do you like? I like both of them (2 choices). I like all of them (>2 choices)
"Either" is similar to "any".
e.g. Which film do you like? I don't like either of them (2 choices). I don't like any of them (>2 choices