Telemetry on Tranmitter help

[RcMark]

I have bought a transmitter and reciever for my quadcopter.
The seller upgraded the tranmitter and in the description it states 'On the back of the transmitter is a switch where you can swap between the different telemetry modes'

now my questions are is what is telemetry in the quadcopter world and what modes could they be??

 

[ringolong]

Telemetry is the reporting of flight information back to the radio such as battery voltage, location, flight speed, height, distance, etc...

I am guessing modes in the context means show different information according to the mode?

What radio is it?

 

[RcMark]

Telemetry is the reporting of flight information back to the radio such as battery voltage, location, flight speed, height, distance, etc...

I am guessing modes in the context means show different information according to the mode?

What radio is it?

This is part of the description:-
I have converted the X-378 transmitter from 35mhz to 2.4ghz! Using the Frsky DHT 8ch Telemetry module. I have also added the 5 db antenna for extra range!!!
This transmitter comes with a D8R receiver (telemetry capable).