The difference between the big dipper and the main one.

There is no difference. Grandpa Beidou generally refers to the Big Dipper, which is located on the spoon-shaped map of Ursa Major, and can point out the direction for people on earth. In ancient China, the worship and belief in the Big Dipper even surpassed the sun and the moon, and only the Big Dipper could point out the direction at certain times.