What is Parachain Slot (Polkadot and Kusama)?

Parachains are Polkadot-based independent blockchains that connect to and run off of the Polkadot network's main Relay Chain. Parachains can also be considered shards (with entire blockchains inside them). Parachains run in parallel to the Relay Chan and process transactions through parallelization by using sharding and exhibit extremely fast transaction times. Parachains are able to host their own blockchain-based tokenized assets within their independent network and control their own governance processes by paying to use a parachain slot by attaching to the main Relay Chain.