This is a rather obvious hint – at least with hindsight – but someone might find it useful. If you’re like me, you may have a bunch of short elisp files with various small utilities you have written yourself in the past few years. For some reason, you may not want to load them at startup (maybe you want your Emacs to start as fast as posibble, maybe you don’t want to pollute the namespace with things that are only occasionally useful…). Then, you might want to say
(add-to-list 'load-path "~/path/to/your/utilities/directory")
in your init.el, and be able to quickly load them using load-library (using autocompletion). Maybe you even want to be able to find them fast – then, you can use find-library.
Also, if you don’t care about the finding stuff, only the loading, you may leverage another mechanism present in Emacs since very old times: autoloading. This is completely another story, though, and I encourage you to read the relevant portions of the manual some day.