What is an 'Epoch' in Cardano?

Cardano is a peer-reviewed project, similar to Ethereum. Its developers, however, claim that it is more efficient and decentralized than Vitalik's project.

It uses Proof-of-Stake for consensus, employing an exceptional innovation called time slots and epochs as part of their Ouroboros Praos protocol. This is vital in reaching consensus where validators play a crucial role.

Cardano splits their transaction settlement and validation times into periods called epochs. As of August 12, each epoch lasts for about five days. 

A snapshot is created at the beginning of every epoch—a record to mark the redistribution of ADA coins staked in the last epoch. 

The snapshot determines the total stake pool and the chances of a slot leader getting a chance to verify a block. Slot leaders, in turn, are selected randomly from the over 1k Cardano staking pools. Every epoch comprises 432k slots. Each slot lasts for a second. The higher the stake a pool controls, the more the chances of selection and reward. Note this; there are 21,600 nominations per epoch as a node is selected every 20 seconds.

Epoch rewards are distributed until the fourth epoch from the following snapshot.