The symbol “?” shows that two values are not equal and that they do not represent the same thing. For example, “a ? b” means that a is not equal to b.
Inequality in mathematics shows that two values are different. The symbol “?” does not show that one value is greater than the other or that the two values can be compared in size. The symbol just shows that the two are not equal. Other symbols for inequality are "<," ">," "?," "?," "?" and "?." These symbols are used if the given values are elements of an ordered set and can be compared in size. For example, 8 "<" 9 which reads as eight is "strictly less" than nine.