The Elrond blockchain platform is designed to be a public development infrastructure that will be more secure, efficient, and scalable than other blockchain platforms. The Elrond blockchain is aimed at DApp developers and enterprises. Elrond will have a Prof of Stake consensus mechanism, and will include an Adaptive State Sharding feature that will allow multiple validators to process transactions in parallel.

Infura is a DApp infrastructure provider that was created by ConsenSys and gives developers the tools to securely access Ethereum and IPFS. Their API enables users to set up Ethereum Nodes, and then install, configure, and maintain the Ethereum infrastructure more easily, and at lower cost. Infura was originally created by ConsenSys.

Holo is a decentralized hosting provider that is built on top of Holochain. DApps can be set up and deployed with Holo hosting, as a decentralized alternative to Amazon Web Services, or other centralized hosting solutions.
Holochain is a protocol for creating decentralized Apps and is different from blockchain protocols in several ways. The main difference being that Holochain takes an agent-centric approach to their consensus mechanism, and has a different approach to validating value transfers.
The HOT token is used for paying for hosting services on Holo, and users can be paid for offering their computing resources.