Webbing Double Wrap is where you wrap a piece of webbing twice around the anchor and tie the two ends with a water knot. Then you attach a quick link to both loops. Similarly, for the tripple wrap, you put the quick link through all three loops.
The double or triple wrap distributes the load to each strand of webbing to that each strand only has to resist a portion of the load. This is called "equalized" rigging. It also spreads the load out on the bark of a living tree, reducing damage to the tree. As opposed to the Wrap 2 Pull 1, this method does not cinch around the anchor, so it could still slide up or down, but it also won't strangle the tree if it is left there for years.
The double or triple wrap is not redundant. If there is a failure in any portion of the webbing, the entire rigging will fail.