Hyperledger is not a cryptocurrency, a blockchain or a company.

It is a project under the Linux foundation like NodeJS.

Definition:

Hyperledger is an open-source community of communities to benefit an ecosystem of Hyperledger based solution providers and users focused on blockchain related use cases that will work across a variety of industrial sectors.

In simpler terms, Hyperledger can be thought of as a software which everyone can use to create one's own personalized blockchain service.

Restrictions of public Blockchain:

Public blockchains require each peer to execute each and every transaction and run 'consensus' at the same time and are therefore not scalable and do not support Private and Confidential transactions.

Differences between Hyperledger and blockchain:

The "peers" are now 2 separate runtimes with 3 different roles (Endorser, Committer, Consenter).

Committer - Responsible for appending validated transactions to their specific ledger.

Endorser - Responsible for simulating transactions and preventing unstable and non deterministic transactions.

Consenters - Responsible for Network's consensus service. A collections of consensus nodes (CSNs) will order transactions into blocks according to the network's choses ordering implementation.

Hyperledger Projects:

Hyperledger Sawtooth, IROHA, Hyperledger INDY, Hyperledger Fabric.