Latin for things to do (from ago = I do).
Often used as a plan or program for a meeting, typically having a structure similar to this:
Contrary to popular belief, the word agenda does not imply anything devious, such as the overthrow of the government or forcing the ideology of the group on everyone else. Nevertheless, in English it is often used to imply just that, often in a paranoid way, that is, assuming there is a hidden agenda, that is implying a group has an official list of things to do which appears in the minutes, and another top secret one that is really discussed at a meeting but not recorded in the minutes.
Or, in the case of an individual, the idea that the person says one thing but really wants another.
Though that may happen, the claims of a hidden agenda are generally similar to the reports of Mark Twain's death during his life, i.e., highly exaggerated.
The real meaning of the word agenda simply is an action plan, literally things to do, nothing more and nothing less.