What does legislation mean?

The term "legislative" is the adjective form of the noun legislature (law-making body).

The term applies to groups that "make laws", as in the US Congress or the UK Parliament. Legislative bodies are usually made up of elected representatives from states, provinces, or territories, who are called into session to investigate, propose, approve, amend, or rescind the laws of the political union. A majority or more of the total body is required to agree on enacted legislation, subject to review by the elected Executives, or by the judicial branch.