What is Cosmos?

Cosmos is a decentralized network of independent parallel blockchains that can scale and interoperate with one another. Cosmos is built on a Proof-of-Stake consensus mechanism. It uses a Proof-of-Stake consensus mechanism, in which validators rather than miners validate transactions and verify the accuracy of new blocks.

Cosmos is often referred to as the "Internet of Blockchains" because it enables blockchains to connect and communicate in a decentralized way using inter-blockchain technology (IBC). You can think of Cosmos as a huge network of interconnected tools that are modular, adaptable and communicate with each other as lego blocks to build a greater whole than their parts.

Blockchains built in the Cosmos ecosystem are called “zones”. Cosmos zones do not necessarily need to connected to one another, but if they choose to, they have the ability to validate and keep record of each other using "light clients". Each zone can function on its own: it can authenticate accounts and transactions, create and distribute new tokens, execute changes by governance, and many other state transitions enabled by the Cosmos SDK modules.

Stride is a Cosmos zone. It is connected to the Cosmos Hub and many other Cosmos zones. Stride uses a new version of IBC ("IBCv3") to communicate, transact, and interoperate with other chains in the ecosystem. Stride is the first zone to use Interchain Accounts and Interchain Queries, two core IBC technologies.

Sources:
Cosmos Network
What is Cosmos?
About Cosmos
What is Cosmos? A beginner's guide to the Internet of Blockchains
Why Blockchains Need Cosmos Proof-of-Stake for a Sustainable Environment