What is lynching? and what is the.....?

what exactly was lynching used for? what was the point of lynching? i'm doing literature, and we studied the poem the lynching by Claude McKay. we were given a brief view of what it was, and i decided to look it up. however, i still don't understand what really was the point of it. so if someone can kindly explain, without making racists comments it will be greatly appreciated.