All Razer mechanical keyboards feature Cherry MX switches. The diagram on the left illustrates the Cherry MX Black switch which has an actuation force of 60g (80g overall), and is a linear switch meaning it has no tactile feedback. The diagram on the right illustrates the Cherry MX Brown switch, which is what the Razer Black Widow Stealth utilizes. It switches have an actuation force of 45g (55g peak). The reason this board is dubbed "stealth" is for the simple fact they switched from the Cherry MX Blues used in their other boards that produced that loud "clicky" sound as you depress the switch.
If you want some further information on Cherry switches or mechanical keyboards in general check out