The integrate command computes integrals and antiderivatives.  It is located on the F3 Calc menu #2.   It can also be found on the face of the keyboard above the 7  key
(2^nd 7.)
 

Antiderivative.

• Remember:  You must ALWAYS specify the variable parameter.  The calculator must know with respect to which variable you are integrating.  This is true even if there is only one variable in the problem.

The nInt command computes numerical integrals.   You can find the nInt command under
F3 Calc #B nInt(.

     
      

Notice the syntax.

This command is the same as using integrate with APPROX mode