If you're genuinely curious, you really do need to download the free demo of the game "Kerbal Space Program". You really can't grock space travel & orbital mechanics unless you play around with them.
Ideas like "faster is higher, slower is lower", and "burn at the low point to change the high point" don't make sense until you play with them. That and, there is no such thing as a straight line in space. Everything's an orbit.
Seriously, give it a try. You might just learn more than a year of college by just paying a game.