While shareholders may pass decisions at general meetings they can also pass certain decisions in writing, using a written resolution, without calling a meeting. This process involves circulating a written resolution amongst all shareholders entitled to vote (ie who own voting shares at the time of circulation). The written resolution will pass when the necessary threshold for the resolution is met.
Certain resolutions cannot be passed as written resolutions, including removing a director from office before the end of their contract.
For more information, read Written resolutions.