It is shorthand for:
netsh int ip reset resetlog.txt netsh i i r r
The last ‘r’ being the “log file” that you really don’t care to read.
What does it do? It hits your TCP/IP stack with a sledge hammer. And forcefully rebuilds it via a rewrite of two Registry keys:
This has the same effect as removing and reinstalling TCP/IP.
Please do this command in an Administrative command prompt