The only difference is the size.
A standard full-size mattress measures 53–54 inches wide and 75 inches long. A standard queen measures 60 inches wide and 80 inches long. The width of a full-size mattress tends to be best suited for a single sleeper or a sleeper with a pet or small child.
Couples who like getting cozy may also enjoy sleeping in a full, but otherwise, the mattress is too narrow to accommodate two adult sleepers comfortably.
A queen mattress is longer and wider and makes a more comfortable choice for two adult sleepers. But it also takes up more space and comes at a higher price than a full mattress.