The ParaID (Parachain ID) is a unique identifier for a parachain or parathread on the Polkadot, Rococo, or Kusama networks. To reserve a ParaID, follow these steps:
Polkadot-JS comprises a suite of tools that interface with the Polkadot blockchain, its parachains, and testnets such as Rococo in detail. If you are new to Polkadot, referring to this guide is recommended.