On Skyblock, everything rotates around your island level. Your cobble generator depends on your island level, and the /island challenges need a certain island level to progress to the next set of challenges. As well as that, the Skyblock competition is based off island level as well.
On Skyblock, each block has its own value (points). The harder it is to get that block, the more points it gives, and the easier the block is obtained the less points given.
The basic element of Skyblock is the cobble gen. On NRG`s Skyblock, when your island level increases, you unlock new resources in your generator. The command to check the generator level is /is generator level to see your current gen chances, and /is generator levelsall to see the chances from 1 through to 8000.