What 2 groups are cancer placed in?

Your query relates to two basic types-

(i) Benign:which simply forms a tumour, which is surrounded by a tough capsule. The surrounding capsule prevents the cancerous cells from spreading. Hence it can be safely cured by surgical removal of the tumour. As it is not fatal (killing, if detected early of course), it is called benign (= friendly, although no cancer can be considered friendly.)

(ii) Malignanat: In t his case the tumour is not surronded by the capsule, hence the cancerous cells are loose, amorphous mass . Therefore they can spread in the surrounding tissues and provoke the noncancerous, healthy cells to behave as cancerous cells. As in this case, as there are very few chances survival, most patients are unfortunate.