Possibly most commonly to send sensor data across.
Typical range: about the same as WiFi (same frequency).
I use them for radio control for model trains. And I have some installed in my own trains for battery powered radio control.
I have tested a pair of the low power nRF24 modules (with PCB antenna) at a range of 110metres outdoors
Simple nRF24L01+ Tutorial
Excellent. Presumably with a pretty small Arduino like a nano or perhaps a processor chip on a purpose-made pcb?
On that though @Robin2, the library (from TMRh20, v1.3.1 as installed via Library Manager), examples only include RF24.h, while you include RF24L01.h as well. What's that about?
I use an Attiny 1634.
Do my examples work for you?
So is that the ATtiny soldered on an nRF24?
I fixed it upside-down on the nRF24 with a double-sided sticky-pad.
I use the nRF24 pins for connecting
Talking of which, I see the nRF24 is another example of non-breadboard-friendly pins
Because use in breadboards by Arduino experimenters is a ridiculously trivial part of their usage.
Just get some adaptors.
Dupont cables are an easy way to connect the nR24 modules
(Well, generic Dupont "style")