Interchain Security
interchain-security houses the code for implementing Interchain Security: https://blog.cosmos.network/interchain-security-is-coming-to-the-cosmos-hub-f144c45fb035. The repo is currently a WIP and targetting v1 of Interchain Security.
CCV stands for cross chain validation and refers to the subset of Interchain Security related to the staking and slashing communication between the provider and consumer blockchains. The provider blockchain communicates staking changes to consumer blockchain(s), while the consumer blockchain may communicate slashing evidence to the provider blockchain.
The code for CCV is housed under x/ccv. The types folder contains types and related functions that are used by both provider and consumer chains, while the consumer module contains the code run by consumer chains and the provider module contains the code run by provider chain.
NOTE: At the moment the testing app may not be functional, please rely on the IBC testing suite to write unit tests for the moment.