Yeah, if you are relatively new to audio production it is very much worthwhile to learn about using busses to achieve different things. Mixing like this is one of the more obvious and basic uses but they are incredibly useful and even crucial to getting things done. For example if you want to apply reverb to your mix you don't necessarily want to use a different reverb on every track. You would create a buss, put the reverb on the buss then use sends or the main output on the tracks to point toward that buss. Now the reverb is applied evenly and any changes you make to the reverb settings will affect all the tracks. If you use sends then you can mix in how much reverb each track gets. EQ, delay and compression are other effects commonly used on busses.
As far as quick grouping in SOnar it is a super easy way to make any kind of change to multiple tracks at once like outputs, gain, pan, solo, mute, record, etc... so it is another very important thing to learn to save yourself time and hassle. Cheers.