What? you spent 42$ on this? Who sold you that? that stuff is free!
Anyways. Here's a rundown:
1. On your xbox there is currently a dashboard installed. The green one is called "M$ Dashboard"
2. When you load the exploited savegame, you use a loophole in the gamecode to execute "unsigned code", which are programs made by people that do not work for any game company.
3. This unsigned software is also called "dashboard", but has other names (UnleashX, EvoX etc.) and gives you more access to the harddrive. Krayzie's installer then moves the M$ dashboard into a seperate folder, and basicaly replaces it with another one (EvoX or UnleashX) that allows the execution of unsigned code without needing to load the exploited savegame. (It's a little bit more complicated than just a replacement, as the new dashboard is only signed with the habibi key, and the box would refuse to boot that. That's what the fonts are for, but that's a little bit too technical now and we want to keep it basic, now don't we?)
4. After you installed the softmod (new dashboard), this is the thing that boots up when you turn the box on. Krazies installer also hides the drive partition the dashboard is on, to keep you from accessing (and damaging) it. You can now run unsigned code, which is burned games, emus etc.
Advantages: Run unsigned code, costumize look, no need to open box
disadvantages: If you mess it up afterwards (which is very unlikely to happen, actually), it is harder to recover than a with a modchip, No access to LIVE! dashboard (however, the LIVE service is still usable).