With digital storage (on hard drives, on external media or in the cloud) being so cheap these days, I suggest creating multiple copies of some files.
For example, if you went on holiday to the Isle of Skye with your friend Percy, any photos you took of Percy during that trip can be filed both under 'Isle of Skye April 2019' and under 'Percy'. Similarly, pictures you took of the alpine pearlwort on the island can be stored under both ''Isle of Skye April 2019'' and 'Wildflowers'. Some images might best be stored within three or more folders.
It's also possible to tag each picture with relevant terms, and then search by tags, but personally I don't think that it's worth the effort.