In this lesson we explain the GAMS commands in some detail. We have assumed that the reader has some practice with GAMS programs, because this lesson has been written under that assumption. In fact, this contains some material that must be consulted after some time has been dedicated to previous lessons, in which the students are assumed to be developed several examples of GAMS programs. All commands are explained in detail and some examples are given. We complete the lesson dealing with the conditional operator and the use of dynamic sets, including its capability to work with unions, intersections, differences and complements.