What is commonly referred to as a skin tag. they can be easily removed by burning or freezing at a clinic or simply but tying thread round their base until they fall off. 90% of people get a skin tag at some point in their life in particular its more prevalent in the old and fat. Chafing is purported to be their main cause hence why they often appear in the groin and armpit folds. They can come back after removal but usually don't although you will often get another one in the same rough area.

Tl;dr its no big deal just need to get them removed.