A repository, or "repo" is a library of software made available online. Maemo has three main repositories (see extras). Debian has a manual on how to use repositories, which is relevant because maemo applications are distributed using the Debian package system: same system, different repositories and software.

Starting with Maemo 5, the only supported way to install software is from repositories using the built in application manager. However, no knowledge of this or understanding of repositories is necessary for end users. The downloads page lists the applications in the extras repository and handles everything to install automatically with a click.