The gross loan is the figure the facility is written for. The net loan is what actually reaches you, after the arrangement fee and, on a retained interest deal, after the interest for the whole term has been held back at the start. Two lenders quoting the same gross figure can leave very different amounts in your account, which is why offers are compared on the net.
Interest is either retained or serviced. Retained means nothing to pay monthly because it has already been deducted, which suits a project with no income until it sells. Serviced means you pay it each month and more of the loan reaches you up front, which suits a property already producing rent.
The exit is the repayment: a sale, or a refinance onto a term facility. A bridging lender is lending against the strength of that exit far more than against your accounts, and an exit that has not been tested is the most common reason a bridge ends badly.