Items are classified by the brain and stored in categories by the brain. It is because they are searching down a pathway which is not connected to the word which they are searching. If they were search for the word yellow, the word might be in the part of the brain with words which start with yellow. It might also be classified as a word with l's in it. Each time an item is stored and cross referenced in the brain, a new pathway to that item is sensitized.
Many people associate a memory when listening to a particular song.
Each time that song is heard, the memory is relived. The same can be said of smells. A particular smell might stimulate a specific memory each time that smell is recognized. There are a variety of ways that memories can be labeled in the brain. Memories can be stored with a visual, audio, or other sensory perceptions.