Bought a pair of 700c/29" Velocity Dyad rims and have two questions:

1.) What does the 29" and the 700c stand for?

2.) Considering the size is not listed on the tie (it only says 18-622 - not sure what that stands for, tho' - if anyone has an idea, I'd love to know), how would one go about measuring the rim to insure that the it is, in fact, a 700c/29" rim?