An Annual General Meeting is a meeting of a company's shareholders (unlike a board meeting, which is a meeting of the directors).
Companies Act 2006 Part 13 (comprising 80 sections) provides the statutory framework for the calling and conduct of general meetings.
Note too, that resolutions can also be passed as written resolutions (without having a general meeting) and there is now no statutory requirement for a private company to hold an Annual General Meeting, unless the articles make provision for one to be held.
For any particular company, the statutory rules are supplemented by that company's articles.
Many companies have the provisions of The Model Articles (articles drafted from 1.10.2009) or Table A (older companies), either completely or with some amendment.
The usual business of an AGM is to receive the Financial Statements (Annual Accounts) and directors' report and, in some companies to elect directors and/or auditors.
Even if there is not going to be an AGM to discuss the accounts, the accounts still have to be distributed to the Shareholders.