Too Long; Didn't Read
Tokens like Ethereum, Solana and Polkadot all power their own chains with a common goal of providing a scalable platform for decentralized global apps.
Polkadot in particular enables the use of parachains which are custom, project-specific blockchains that are integrated within the Polkadot ecosystem.
Parachains are considered parallel chains that have their own runtime logic. They also benefit from the shared security and cross-chain messaging provided by the Polkadot relay chain.
While parachains permit a high degree of flexibility and customization, they also require more effort to create and maintain over time.