Individual sessions involves just you and the counsellor/psychotherapist. It often feels more intensive than group sessions because the time is focused entirely on you.
Group therapy involves at least one other person, plus the counsellor/psychotherapist. It can be a useful supplement to individual counselling or a way of making therapy more affordable. Groups can be useful for meeting other people in similar situations. It can be a great comfort to know that you are not the only person experiencing your circumstances. It is also an opportunity to learning from others with similar concerns. Groups can be a great source of relief, strength and inspiration. Groups sessions can also provide a safe environment for you to try out new behaviours or to understand the behaviours of others.