When someone wrongly believe something on sufficient basis then it is false knowledge.
There are two types of false knowledge.
1. Doubt
2. Misapprehension
1. Doubt: In this case a person has belief based on insufficent evidence or reason because if there was sufficient evidence or basis then it would be true knowledge as well as certainty rather belief because there is doubt, therefore such knowledge of person that is based on uncertain or insufficient evidence then it is said false knowledge.
2. Misapprehension: In this case a person has true knowledge but he believes something other thing instead of true knowledge or he has mistaken something to be true, when it is actually false.