Decentralized Web - Q&A

How do decentralised apps created on Ethereum interact with each other? Do they exist on the same network, meaning that the same nodes used to host Ethereum would be used for the apps created on Ethereum, or is it running on a separate network?

The decentralized apps make calls to 1 of the nodes of a blockchain. Usually the Dapps interact through what is written on the blockchain.

Most of the Dapps which call smart contract functions on the Ethereum blockchain access the blockchain through a single (Infura) or few (metamask,quicknode) nodes.

For more please check -
What a Dapp really is