Please help me in electronics?

Question

Can anyone explain with simple illustration the importance of dc load line & operating point.

Why it is used?

Answer 1

See figure 3 in the link

Plotting a load line and operating point at Quiescence (no input signal) allows you to visualize where to bias the input. This point  allows the maximum input voltage swing of the signal and resulting amplification while staying within  the linear region (Class A operation).  

Other quiescence points may be choosen to operate the amp in a region of saturation or cutout (Class AB , B or C).  Using the non linear regions to process only a portion of the input signal.