What is a yoke?

The Mishnah discusses accepting upon yourself the "yoke" of heaven. But what is a yoke?

A "yoke" is usually a piece of wood that harnesses two animals to work together and plow a field. This is usually considered a "hard job" or a burden. As such, when the Mishnah says one needs to accept "the yoke of the kingdom of heaven" upon themselves it is another way of saying that one needs to accept upon themselves the "the heavy burden" of doing the mitzvot as Hashem wishes.