If you and your friend are seated separately on an airplane, you can always ask a stranger if they will switch seats with you. To switch is to change or exchange.
Switch can be a noun or verb, and in most cases it has the meaning of change. You can switch classes, political parties, or the radio station. Sometimes if you switch something with someone, they take yours and you take theirs — as in an exchange or trade. However, there is one unrelated and frightening meaning for the word. In the olden days, a form of punishment was to be hit with a thin, flexible, piece of wood called a switch.