Nostr is a protocol (not an application) like email or http (it's a set of rules that makes browsing www possible) to move data over the internet in a decentralised way.
Nostr is fundamentally different in the way it works
The main problems that Nostr directly addresses in internet applications are identity portability and data portability.
For the last decade or so, countless alt-coin's (read shitcoin's) have attempted to address data portability on the internet, NOSTR is the first one to successfully achieve it.
In 2009, Bitcoin went about claiming the decentralised value transfer protocol. Similarly, NOSTR is setting itself as decentralised data exchange protocol.
and you will shocked to learn that Nostr works because it's too simple. The way the data moves in a simple dumb fashion between the client ā€” relay (think of it like your twitter app & their inhouse servers, although there are no servers in NOSTR)
For the last decade, every altcoin (shitcoin) failed to accomplish this task because while creating their token & the shitcoin, they also introduced a lot of complexities; for example if you want to develop on Ethereum Blockchain, you will have to know/learn the language Solidity; which was created exclusively to build stuff (garbage) on top of Ethereum Blockchain using Smart-Contracts
Nostr is exactly opposite, it's simple transfer of data from clients to multiple (a lot of) relays.
Nostr & Bitcoin together will be the freedom layer of the cyberspace.
I hope this explanation helps, @n057r173! Let me know if you have any other questions šŸ¤ 
ā€” rS7Y