Animation has come so far, exploring such ever-expanding frontiers of elaborateness, realism, and stylization, that truly understanding the medium might require a return to its early years. Luckily, the UCLA Film and Television Archive has made available a selection of preserved shorts from the silent era, free to watch online. You'll find the earliest of these, The Enchanted Drawing from 1900, embedded above. But I recommend watching not this YouTube version but the one on the Film and Television archive's site. There you can select one of four soundtracks — piano accompaniment, a full score, the preservationist's commentary, or, of course, silence — and read notes from preservationist Jere Guldin and historian Jerry Beck. The Enchanted Drawing, Beck writes, "is considered one of the forerunners of animated films to come. It's more appropriately a "trick film," employing stop-action techniques pioneered by Georges Melies to make a sketched face, cigars, a bottle of wine, and a hat appear as real objects after being drawn."
Just above, you can watch the YouTube version of 1928's The Wandering Toy, the most recent film now viewable in this archive of preserved animation. But again, if you watch it on UCLA's site, you can enjoy their range of audio options and program notes. "A sizeable amount of the silent features and short subjects still in existence do not survive on theatrical 35mm film gauge but in the smaller 16mm amateur and home-movie format," writes Guldin, shedding light on the archive's raison d'être, noting that this particular short "was preserved from what is thought to be the only 16mm print in existence." The Wandering Toy, as Beck describes it, "combines paper cut-out animation mixed with live travelogue footage of Sweden, Bavaria, Morocco, Holland, Mexico, India, and Japan. [ ... ] The results are an attractive and unique combination of travelogue and cartoon, certainly quite different from the usual animated fare at the time" — and, I might add, a world apart from, though a clear antecedent of, the high-tech, high-budget, spectacle-oriented animation we see in theaters today.