Vertical collar is the same name as bull call spread, which is the sometimes just called a collar. The naming conventions of option strategies are rediculous and simply cause confusion, what matters is the payoff.
As Richard Feynman sums up about a particular type of bird; you can know the name in any language, but if you don't know what the bird does, the names are pointless.
It's called a collar because you're putting a "collar" on your gains and losses. In the vertical call spread, bull call spread, bullish collar, whatever you want to call it, you sell out of the money calls to help finance the purchase of a put option. This limits your losses (in your situation, a downward gap) and also limits your upside. You also must own the underlying, which in your case could be a stock, future, currency, etc.
It's called "inexpensive" because by selling the out-of-the-money call option you receive premium which goes towards buying the put option.
If you want further clarification let me know.