If you "skimmed" the tour and tutorials and don't know what it is, stop skimming. Then, start reading. This isn't some arcane library you need domain-specific

If you "skimmed" the tour and tutorials and don't know what it is, stop skimming. Then, start reading. This isn't some arcane library you need domain-specific knowledge to understand, it's a system with a purpose and intent that's quite explicitly explained.