Talk back is volume of your voice through an external speaker so you can check how you sound, and delta tune is moving your receive frequency off of the standardized channels to better receive a frequency that's slightly out of tune, you can pretty much leave it in the middle.
Amateur Extra, GMRS (licensed)
Icom 92AD Yaesu FT-7800, FT-2900, FT-270
Icom F21GM, Motorola T7400, T6320
Kinetic SBS-1eR Uniden996T, RS Pro106, Pro-164, Pro-95