A felony is anything punishable by a year or more in state prison; a misdemeanor is anything punishable by up to a year in county jail. Realistically if your friend was charged with felony shoplifting the charge will either be reduced or s/he will be put on probation with some county jail time. Theft can become a felony if the amount taken exceeds $400.
A felony can result in a grant of probation or incarceration in state prison. Theft for less than $400 of merchandise is normally charged as a misdemeanor unless there are other elements to the case, such as prior theft convictions or the person used force while stealing (which would make it a robbery). Your friend should consult a defense attorney to see what can be done to get a good result in this case.
A shoplifting can be a felony either because they have prior convictions (it used to be one prior conviction and the new one can be a felony, but the law has changed and you need three prior convictions now) or they think your friend entered the building with the intent to steal, making it second degree burglary. Both second degree burglary and petty theft with a prior can be charged either as felonies or misdemeanors.
If the police can arrest and book for a felony or a misdemeanor, they'll always choose the felony, even if the DA will only file a misdemeanor. It has to do with funding and statistics for the number of felony arrests they make.