Can someone explain what these terms mean when it comes to inputs and guitar amps. Are they refering to impedances?

 

Nothing to do with impedances. I'm sure you could google for a complete explanation but, in a nutshell, any source with just a ground and a "hot" pin is unbalanced. Typically a 1/4" jack (tip and ring) as used on any guitar I've ever seen.
Balcanced sources , typically microphones from half decent and upwards have a balanced output. This requires ground and two signal carrying leads. A three pin XLR being a common example of a connector, although sometime a 1/4" stereo jack is used.
The advantage of the balanced circuit/lead/input configuration is that it is far less likely to pick up interference (called common mode) if correctly terminated in the amp or mixer.

 

A balanced signal has the same signal on two wires, with the phase 180° apart. This is done to reduce noise picked up during transmission from the source to the destination. At the destination the two signals are put into a difference amplifier which eliminates (mostly) any noise picked up along the way, which will be common to both signals (not out of phase like the signal of interest) and thus attenuated according to the amplifier's common-mode rejection ratio (CMRR).

 

The balanced signals found in the music industry are usually low impedance, but "usually" is just a habit, not a rule.

 

Can someone explain what these terms mean when it comes to inputs and guitar amps. Are they refering to impedances?

Thanks all, very helpful