Cosmos

Tendermint is a PoS consensus mechanism.
ABCI is an interface for how application-specific state will be replicated by a consensus algo. Tendermint complies with ABCI.
IBC is a protocol for how blockchains to communicate with each other
The Cosmos SDK is a library with implementations of Tendermint and IBC, for use in building a new blockchain.
The Cosmos Hub is a specific blockchain intended to serve as a master connector of many blockchains that use IBC

Consensus Mechanism

Tendermint whitepaper ("The latest gossip on BFT consensus") (2018)
- describing the Tendermint consensus algo
Tendermint vs BFT
Jepsen: Tendermint
- real-world test of whether Tendermint actually satisfies its theoretical safety properties.

Cosmos whitepaper (2016)
- Cosmos network whitepaper (describing Cosmos zones/IBC and validator behavior - a network built on Tendermint consensus algo). See "Consensus systems" for a good summary of Tendermint vs PBFT and other consensus algos.
Cosmos & Polkadot comparison (2019)