Substrate

Substrate is a blockchain software development kit framework and a runtime created by Parity that can be used to create blockchains that are compatible with Polkadot, which itself was created with Substrate.

Substrate pallets are Rust modules and support libraries, pre-built components to use with Substrate, the runtime and software development kit used to create Polkadot. You can pick and choose pallets to create blockchains that have the features you want and implement them using the FRAME Framework for Runtime Aggregation of Modularized Entities tool.

Pallets may provide anything from foundational definitions for primitives in the frame_system pallet to advanced functions like those contained in the pallet_alliance pallet, which includes functions to initialize “a collective for community members to join in an effort to establish rules against bad behavior and to provide recognition and influence for teams that contribute to the ecosystem.”