You can drive a car with a slipping transmission however if the transmission is slipping it's an indicator of either low transmission fluid or the transmission is about to go out.
If your transmission is slipping make sure the transmission fluid level is correct because low transmission fluid can be a cause of slipping transmissions.
If the transmission is driven while it's slipping then it can eventually lead to transmission failure and the vehicle will not move at all.
That can leave you stranded on the road somewhere and a big repair bill.
Sometimes the transmission might even need an overhaul and be rebuilt or it could even be just a clogged transmission filter.
Either way take the vehicle to a mechanic or a transmission shop to have the slipping transmission checked out because transmissions should not be slipping at all.