There are different types of firelogs, f.e. 100% pressed wood logs and manufactured logs.
Many manufactured fire logs are made from sawdust and wax. They cannot be used in closed stoves.
Compare to firewood it is easier to start a fire with a log (they can be lit with a single match) and they burn steadily and leave little ash. But on the other hand logs are artificial and don't have the cozy atmosphere of a true wood fire.