Forging a check is where someone illegally uses someone else's check and then signs that persons name to the check and also writing the check out.
For example if you take someone's check and then write in an amount and then sign that check over to you to cash then that would also be forgery of a check.
Or if you took someone's check and then signed it and filled it out to try and make a purchase then that would also be forgery.
Forging a check can get you in jail or prison for a long time and it's very wrong to do.
Forgery involves the making, altering, use, or possession of a false writing in order to commit a fraud.
If convicted of forgery of a check or checks you can face up to 5 to 20 years in prison depending on the state you're in and if it's your first offense or your second or third offense.