In one sentence, describe what the following article is about:

On older Android models, the "Insufficient storage available" error was often a result of a system malfunction--not necessarily an actual report of insufficient storage. Before continuing, verify the status of your phone's storage.  You can check your Android's storage from within the "Storage" section of the Settings app. If your phone has more than 15 megabytes of storage, you may be encountering an error not related to your storage. To do this, hold down your phone's power button, then tap Power Off or the equivalent. Once your phone has powered down completely, press and hold the power button again until your phone's screen lights up. Restarting your phone will reset your system's RAM. Doing so will both speed up your phone and potentially solve the "insufficient storage available" error if the error is unrelated to your phone's memory. If your phone's memory is actually low, you can quickly free up some space by removing any apps you don't need. To delete an app, tap and hold it, then drag it into the "Remove" field (usually the top of your screen) and drop it there. This can include pictures, videos, and so on. Since these files can take up a fair amount of space, clearing out just a few can improve your phone's memory substantially. If you don't want to delete certain photos or videos, you can back them up to Google Drive instead. If your Android has an unused SD card slot, you can purchase and install a Micro SD from online (or a retail electronics store). If you do have an SD card but you're not using it, consider transferring your apps and data over to it. You can do this by tapping an app in the Application Manager and then tapping Move to SD Card.

Summary:
Check your phone's available storage. Restart your phone. Delete any unused apps. Delete unnecessary media. Invest in external storage.