Stand up means standing up; get up. Stand up is also a type of humor show, where the individual performs standing up, that's why it receives its name.
Stand up is a phrasal verb (Idiom or English slang). It is used in other situations, for example, when referring to someone who missed an appointment previously made with another person (in Brazilian slang it would be "to give someone the cake").
Example: "maria stood me up." (Maria kept me waiting or Maria gave me a cake). The irregular past of the verb "stand" é "stood".
stand up comedy
Stand Up comedy is a comedy show, presented by a single person, where there is no type of character. Stand up comedy presentations usually seek to bring an original text, with themes from people's daily lives.
In stand up presentations, the artist does not use any tools, such as sets, characterization, accessories, does not tell ready-made jokes, it is only based on everyday observations.