The “Nutcracker” season is upon us — but what’s a “Nutcracker”? And why should anyone care? Before I ever saw it, the idea of “The Nutcracker” seemed to embody all that was trivial about ballet: overfamiliar hit tunes, dancing children, dancing toys, dancing sweets.

Yet those standard numbers change when you hear them in context. And those children, toys and sweets become moving in a production that takes childhood seriously. The ballet, building brilliantly, is one of the great 19th-century children’s stories.

The original two-act production, in 1892 in St. Petersburg, was the brainchild of Ivan Vzevolozhsky (director of the Mariinsky Theater), Marius Petipa (choreographer) and Pyotr Ilyich Tchaikovsky (composer), adapting Alexandre Dumas’s version of E.T.A. Hoffmann’s story. Compromises, as in so many theatrical ventures, abounded. Tchaikovsky had to make changes and cuts to his original score. When Petipa fell ill during work on the first act, he was replaced by his assistant, Lev Ivanov, who, under pressure, farmed out at least one dance to a colleague. Tchaikovsky died the next year. Further revisions have gone on ever since.