Bundles combine several paid extensions, and sometimes the product itself, at a reduced price. Buying a bundle adds every extension in it to your license, and starts a fresh update period for each of them.
All Extensions bundles
A bundle marked All extensions, including future releases unlocks every paid extension of the product for your license, and every paid extension we release later, without buying them again.
You need the product first
Bundles that contain only extensions are added to your license for the product, so you need to own the product before buying one. Bundles that say Includes the product can be bought on their own and give you the product license too.