Tezos is a self-amending smart contract protocol with modular architecture. In other words, it can be used for self-executing functions and programs, like Ethereum.
Tezos was founded by ex-Goldman-Sachs and Google X research engineer Arthur Breitman. With the assistance of his wife Kathleen he wrote its codebase from the ground up, and the two founded the Tezos Foundation. The motivation to create it was the governance problems in crypto communities: particularly, contentious forking of Bitcoin and Ethereum. By introducing delegated staking and modular architecture, Tezos achieves resistance to hard forks.
Tez or XTZ is the native coin of the network, though colloquially it is also known as “Tezos”. XTZ are needed to keep track of addresses and secure the network through staking. Users can choose validators called “bakers” and lock up their XTZ with them so these validators would work on their behalf and share rewards earned with their delegated stake. This design is also called Delegated Proof-of-Stake (DPoS) and it strikes a balance between decentralization and network security.