do u know any thing about them

hi some one tell me what r these parts name??? and y we use gain in any cricuit ??????

The first is a surface mount capacitor.
The second is a drawing of a potentiometer, a variable resistor

The 1st one is a surface mount Tantilum capacitor 10uF 16V

you have gain in circuits to scale signals to a usable level.

take a record, if you put your ear near the neadle you can hear the sound, but no-where load enough for relaxing listning. Gain increases the signal voltage level and tehn finallt its power level so it can be heard from speakers