Ethereum Classic is a secure, censorproof, reliable, public, trustless and decentralized platform for running applications.
There are computational tasks involved in adding blocks of transactions to the blockchain. Computers on the Ethereum Classic network that voluntarily perform these tasks get a reward of ether. For security reasons, miners compete to complete these tasks first and win these rewards. This effort is referred to as mining.
Mining involves doing computational tasks whose sole purpose is to intentionally make mining difficult! This difficulty is required to secure the network against certain attacks. These tasks involve finding certain numbers related to each block. These numbers are referred to as proof of work information.
A coinbase is a special transaction, in every block, that creates new ether added to an account selected by the miner of that block. It can also refer to the primary account of a user.
Several miners compete to submit blocks to the blockchain. Inevitably some miners will lose the competition. The blockchain references the losing blocks to make the blockchain more secure. These losing blocks that contribute to the security of the blockchain are referred to as uncles. The term comes from the fact that blocks have preceding parent blocks. The losing blocks are not parents but are still related to the parents. Hence they are like uncles.