The classical concerto differs from the symphony in that it does not have a movement that the symphony has. What is that movement?

As a general rule, a classical symphony has four movements and a classical concerto has three. The nature of their respective first movements and finales is likely to be similar in each case. Each genre will also usually have a slower, more lyrical movement. What a symphony will also have, and a concerto will lack, is a movement cast as a minuet and trio or scherzo and trio.