Hedera Hashgraph is a blockchain network that was designed to allow developers to create DApps that require higher throughput and faster settlement. Hedera uses its own consensus protocol that assigns every transaction a consensus time that is calculated as the median of the times at which each node in the network first received it. The network is powered by the HBAR coin.

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.