A block devices is usually a physical device that’s used for storing data, e.g. Hard drives and solid state drives. A partition is basically a way to organise a block device’s storage into smaller segments, that means creating partitions allows you to use a percentage of your block device’s storage space for a specific purpose and leave the rest available for other uses.
Swap disks are a special type of storage that are used to act like extra system ram. This is handy if your machine is running low on ram, although using swap can degrade performance.