A call spread is a position comprised of long calls and short calls.

A debit call vertical is a bullish strategy that is long one call and short another call at a higher strike. This can be a good play to make if a security is about to test support, such as a Put Wall. Since the max loss is already defined by the price of the debit paid, this defines risk in a way that a stop loss would, but with the added benefit that it cannot shake you out of the trade. 

A debit call vertical is mostly a directional strategy. The max profit of a debit call vertical is the distance between call strikes minus the net debit paid. The max loss is the debit paid (the total upfront cost of the spread).

A credit call vertical is a bearish option strategy where one call is sold and another call is bought at a higher strike on the same date. This is sometimes called a bear call spread. 

Opening a credit call vertical after the breach of a Call Wall is an example of what can be a high-probability trade. 

A trader would primarily use a credit call vertical if they were expecting any outcome except for the underlying price of the security to move up significantly. This is more of a “not bullish” trade than a bearish trade.