Memories and information are stored in the brain like files in an office. Stacks and stacks of irrelevant bullshit stored right next to stacks and stack of useful knowledge, however they are rarely confused. Unfortunately, there is no governing form of organization like alphabetical order or topical arrangement, but the thinker is still confident that after flipping through pages and pages of bullshit they will come to the idea/image/fact/etc they were looking for.
Person 1: "I love looking at leaves in the fall."
A person with Catalog Memory: Flips through the molecular process of photosynthesis, looks at the person, thinks about where their shirt was made and what language those people speak, imagines having sex with person 1 and where they would do it, thinks about photosynthesis again, then finds a memory relevant to the original comment. After about 10-20 seconds, person with catalog memory says: "My family and I used to take a road trip down the river every year. We'd stop at a bunch of parks to look at the leaves."