Aggregation Bits
Bit representing validator(s) within the committee participating in the aggregate signature.

Beacon Chain
The beacon chain stores and manages the registry of validators in Phase 0.

Beacon Block Hash
Blockroot hash of the assigned slot.

Beacon Committee Indices
Validators assigned to this committee.

Block Proposers
Validators chosen at random to propose blocks for validation/attestation.

Committee Index
Index of the attesting committee.

Crosslinks
The only reference of the shards in the beacon chain and a summary of the shard’s state.

Deposit Contract
Validator makes a deposit of ETH into the deposit contract on ETH 1.0 in order to register as a validator on the network.

Epoch
A number of slots (currently 64) after which validators are reshuffled in committees.

Ethereum 2.0
Ethereum 2.0 (ETH 2.0) is the next phase of Ethereum shifting from a Proof of Work to Proof of Stake consensus algorithm. ETH 2.0 will improve issues from scalability, security, and usability for the network. Phase 0 being the first phase for ETH 2.0.

Finality
A block is declared final and can never be changed after a small period of time. All the transactions in that block and all previous transactions are permanent and immutable.

Phase 0
Phase 0 is the first stage of the Ethereum blockchain upgrade and marks the first stage of Ethereum 2.0. Phase 0 implements the Proof of Stake consensus mechanism by managing the list of validators with the launch of Beacon Chain.

Phase 1
Phase 1 is the second upgrade to ETH 2.0 and involves the integration of shard chains.

Sharding / Shard Chains
Sharding is a form of database partitioning wherein large databases are divided into smaller "partition" to reduce data burden and improve scalability. On ETH 2.0, sharding will take the form of 64 chains running alongside the beacon chain, increasing overall throughput and scalability.

Signature
Aggregate BLS signature of the attestation.

Slashing
Slashing involves the deduction of validator’s stake if a validator is found guilty in breaking the rules in consensus mechanism of the network.

Slot
Slot the beacon committee is assigned to attest.

Source epoch
Last justified checkpoint during the assigned slot.

Target epoch
The checkpoint being justified to be the chain tip.

Validator
A validator stakes 32 ETH into the validator-deposit-contract in ETH 1.0. Validators propose and attest new blocks on the network and participate in maintaining the network. A validator is rewarded in ETH as a percentage of their stake when chosen to attest to the a block.