A single stage press is used to perform one reloading operation at a time.  One die is installed, then all of the brass is run through that die to complete the operation, then the next die is installed for the next operation, and so on until all the brass is loaded.

Turret presses allow all of the dies to complete all operations from depriming through seating the bullet and crimping to be installed and adjusted at once, then the brass is processed one operation at a time until complete.  After one operation is complete, the turret head is turned to line up the next die over the shell holder and ram for the next operation, and then repeated until the brass is processed into loaded ammo.

The LEE Classic Turret press is a hybrid that uses a turret that advances automatically so that all operations can be completed on a single piece of brass.  It can also be used as a standard turret press with the advance feature disabled.

Next up are manual advance progressive presses.  All of the dies to complete all operations are installed in the tool head, and all dies engage a piece of brass with each pull of the handle.  That means you can deprime and size in station 1, flare and primer in station 2, drop the powder charge in station 3, and seat the bullet in station 4 all at the same time.  After one cycle of the handle to complete these operations, the shell plate is turned by hand to advance the brass to the next operation.  (This is just a typical example that can vary according to the details of the press design.)

Automatic advance progressives do the same thing as the manual advance machines except the brass is advanced automatically with each pull of the press handle.

There are some variations on using the progressive presses in a single stage mode that is handy for the new reloader while learning each individual operation.