Capital gains

My investment account, like most, I assume, has a depository for transactional cash. This is where any funds which are deposited to the account stay until they are allocated to equities, etc. This is also a place where money is held once positions are sold prior to withdraw from the investment account should I choose to.

I hope this makes sense, because my question is : are capital gains, realized once an equity or other position is sold and that profit is transferred into the holding depository or are the gains realized once that money is completely removed from the investment account?

This is a basic run-of-the-mill individual investment account.