Recollection is either the process of remembering something or a specific memory.
If someone says, "To the best of my recollection, I never met Ted," they're saying they tried to remember Ted and couldn’t. Basically, your memory is your recollection. You can also say your memories are recollections. You could have a recollection of a baseball game on your birthday. If you know that collecting is to gather things, it makes sense that recollecting is like the process of gathering your memories.