The group that a frequency is in is determined by the Memory Number you store it in , when you store the frequency.
Around home, let's say you store those frequencies in Memories 00-99. These are now in Group "0". Around Home, you do Group Scan on Group "0" by selecting one of those Memories ( 0-99) and Start Scan.
When you travel to area "A", lets say that you store those frequencies in Memory Numbers 500-599. These are now in Group "5"
I picked those so if you have more than 100 frequencies in your home area. In that case, you can put more Home Area frequencies in group 1 in Memories 100-199. Then, you can LINK Groups "0" and "1" and all 200 "home" area frequencies are scanned together (0-199).
Hope this helps.
73, Steve, K9DCI