If you are talking about the ones in 'Edit' they are used to indent the lines which you want to stress.
Such as in a recipe Hub (just for an example):
Use the following steps:
1. Mix the dry ingredients
2. Stir in the water (etc.)
It will automatically indent and insert the number or the bullet, depending which you choose. A bullet is simply a large dot placed where the number is.
To use these you go into 'Edit' and just to the right of 'Paragraph' you will see the numbers and bullets. Click on these alternately to see what they look like and get to know them.