Where can I find GNU Radio examples?
The best way to start to understand how GNU Radio works is to look at examples. Under Linux, they usually get installed /usr/local/share/gnuradio/examples or in /usr/share/gnuradio/examples . There are literally several hundred example files to discover, sorted by topic.
What can you do with GNU Radio?
GNU Radio has been used for a huge array of real-world radio applications, including audio processing, mobile communications, tracking satellites, radar systems, GSM networks, Digital Radio Mondiale, and much more - all in computer software. It is, by itself, not a solution to talk to any specific hardware.