This doesn't add anything directly - instead this adds 3 base packages that mods can use to transfer items and fluids between blocks.
Quick overview (for developers):
Attributes: These are available on blocks that implement "IAttributeBlock"
Item and fluid management are both based around 5 similar attribute classes: ItemFixedInvView, ItemFixedInv, ItemInvStats, ItemInsertable, and ItemExtractable.
More details can be found on the wiki.