When you trip, you stumble or lose your footing. As a noun, a trip is a journey or outing, like your trip to the library yesterday or your trip to Japan last summer.
You can trip over a bump in the sidewalk, and you can also trip another person, or make them stumble (although it's not very nice to do so on purpose). The 14th-century meaning of the verb was "tread lightly and nimbly, dance, or caper." Experts aren't quite sure how trip got from that to "awkwardly stumble."