To Do activities are a catch-all for everything that you need to be done that isn't an application or a scouting activity. A great example is picking rocks - it's neither application nor scouting, but it still needs to get done!
Here's everything that you can do in a To Do:
Schedule an activity or record a completed activity
Send out email notifications about your activity
Add pins to mark locations
Add notes
Do you have any questions? Let us know at support@mfm.ag and we'll be happy to help you out!