The last airplane I flew that had something similar was a DA40, it was confusingly called CWS there. Now on my 737 CWS is basically the 'Airbus mode', set a pitch or bank (>6°) and the airplane will maintain it after you let go of the controls. You can also use it mixed with other A/P modes, you could have LNAV as a roll mode while still controlling pitch manually through CWS or MCP speed as pitch mode and fly the airplane manually in a lateral sense...