Essentially, this allows you to craft any item you can craft with the items you have in your inventory. So, for example, if you have 3 diamonds and a log you can click on a diamond pickaxe and it will craft it for you, leave the 2 planks and sticks in your inventory too.
So, it's basically like Crafting Table 2/3. However, what sets this apart (other than working with the latest versions) is that it's a client side only mod. The server doesn't need to (infact shouldn't) install this for you to use it. This means you can play on any server (vanilla might work, haven't tested) and be able to craft with a single click.
I don't recommend using it yet to be honest. It's very buggy and you may loose some items. At this stage it only supports Minecraft 1.6.4 (because the server I'm playing on uses that). 1.7 support will come when it's done.