What does *:before and *:after do in css

Importance of not eating If your doctor has instructed you not to eat before the operation, it's important that you do not eat or drink

before this committee on Saturday , and I did not know until this morning , a few minutes ago , the subject matter that was desired to be inquired into , or

before after It will happen before you know it You try to be nice to them and before you know it, they'll be taking advantage of you (

before So in Selectors Level 3, they decided to change the syntax for :before to ::before (and for legacy reasons, we can still use :before , but it is