What does "suspend group" mean?

Yes, of course we know! The official explanation goes like this: 'A global toggle to suspend the auto-selection of groups. This allows individual selection of clips within a group'.

So if you set up a group, and try dragging it, the whole group goes. This is fine, until you want to move the clips around within the group, but without ungrouping them. If you toggle the 'suspend groups' option, you'll find that you can select an individual clip within a group, and move it. Redo the toggle, and they'll all move together again.

Sometimes useful, but admittedly not very often.