This document about Ethereum briefly explains how decentralized Apps work:
To connect to the network, [people] installed a special program called Mist. (...) Every participating computer receives a reward for their work, because they paid for hardware, electricity and shared their processing power. [They get] a digital asset called ETHER.
Is it true, and is that what is called mining? (I might be wrong but I believe mining is actually more complicated than installing Mist and helping dApps run.)
Also, I installed Mist and would happily share resources to make decentralized Apps work, as explained in the aforementioned document, but I don't see any ETH coming to my wallet... How does it work, did I misunderstand something?