Cash bar vs no-host bar
They mean the same thing: no-host just means the host isn't paying for the drinks. Most cash bars take cards as well as cash.
Why venues charge a bartender fee
The venue earns the drink sales, but if sales don't reach an agreed amount, the host may pay a bartender fee or make up the difference. The terms are on the BEO.
Tips at a cash bar
Guests tip per drink, as they would at any bar. Tips at an open bar tend to be lower, which is one reason some hosts add a gratuity to the bar bill.