Relative truth: What is true for me is true for me, may not be true for you.
If I say, I am now writing in Spanish, most people, who can distinguish Spanish and English, would disagree.
There is an absolute truth here: Spanish and English are 2 different languages.
But, to those who don't know this truth (difference between English and Spanish), both the languages will sound the same. That is relativism. It's a myth.
I have heard people saying "You can't know anything for sure." Well, the question I want to ask them is "How do you know THAT for sure?"
A lot of modern philosophy and liberal theology are built on relativism with an agnostic notion that we can't know anything for sure.
I remember, during my college days, when the professor ask us to solve a mathematical or science problem, the problem will have several variables, but there is always at least one constant. Without that one constant, it is impossible to solve that problem or any problem.
There has to be absolute truth, otherwise everything we believe, say or do is in total vain. We cannot exist without absolute truth.