Mastodon is a component of the “Fediverse,” also known as the “federated universe,” which is a group of unrestricted, decentralized, and loosely coordinated servers.
Tornado Cash is a fully decentralized, non-custodial, open source cryptocurrency tumbler that functions on networks that are compatible with the Ethereum Virtual Machine.
There are multiple apps stores available on Android which can make it a bit confusing to know what each one might be used for.
Android has a ton of Open Source Apps available. Some are good, some are not so good. This video cover 3 of my favorite Open Source Android Apps I use on a daily basis.