A presidential pardon means that any crimes that the person committed (whether they are currently in jail for it, or are hiding in another country to escape punishment) are removed from their record and they will be freed or not arrested and punished for their crime if they return to the country. As the name implies, they were given out by the President of the United States, and unfortunately, our last President pardoned some people who didn't deserve it, and it seems as though he was bribed to do it.
Oh, and btw, that pardon looks fake as hell. His middle name isn't bubba, and he wasn't still president on the 20th (the inauguration was on the 20th, billy left on the 19th).