Modules can include daily spending allowances, amounts that can be spent without the approval of other owners, recurring transactions modules, standing orders that are performed on a recurring set date, e.g. paying your rent, and social recovery modules, which may allow you to recover a Safe in case access to owner accounts were lost. This is just a short example list of possible modules, and one can think of many other modules that could be beneficial to your wallet. Modules enable developers to include their own features via a separate smart contract.