百姓 refers to "ordinary people" as opposed to royalty, officials, aristocrats, and other powerful and wealthy people. 人民 is a more neutral term that means "the people (of a nation)". Example: "二战期间，英国全国人民，不论阶级，都团结起来，奋勇抵抗纳粹军的侵略。".

人民 usually is a political concept ,but 百姓 usually means chinese

人民 = народ 百姓 = люди как простолюдины

There's no difference.人means people,民means more like common people,together it means common people.百 means hundreds,and 姓 means surnames,together it means hundreds and thousands of surnames,in other words,common people.

人民 all chinese beyond rulers . 百姓 all chinese beyond fat cats and rulers