Literally, it's what happens when something is a barrier that catches your feet and causes you to fall. My dog ran into my leg and tripped me up. I tripped over the dog. I went to the bathroom in the night, and didn't see the shoes by the door, so they tripped me up. (I tripped over them.) And you can use the same phrase for any situation where you have a small failure due to something that happens, or something that someone says. The job interview was going really well, they didn't know I was lying about my experience, but then they asked a question which tripped me up.

It means to cause somebody to trip (entangle one's feet). It could be in a figurative or non figurative way. For example: He tried to release himself while being a prisoner, but the rope tripped him up. Also, to make somebody make a mistake. "Don't interrupt me when I'm talking! You're tripping me up while I try to explain what happened". In Portuguese something similar would be "tropeçar"