A homepage is a web page set as the startup page on a browser. You can set any page as your homepage and change it whenever you want. However, some browser extensions or even programs you install on your computer, might change it without your permission, nor consent.
These tips will help you set the homepage you want in a safe way, without altering any other settings.
Please note that some browsers on Android and iOS smartphones don't have the homepage option yet, but they might add it in a future version.