"Absolute truth" is either absurdly simple or extremely complex, and not a lot in between. There are some truths that are so reliable that even should they be "disproved", they're only disproved by "a little bit". For instance, Einstein didn't revoke Newton's Laws of Motion, he just tweaked them a little bit so that they worked with electromagnetic theory.
Many truths are relative and conditional and apply only in certain circumstances. For instance, thermodynamics is extremely accurate and reliable, but only because it's essentially doing statistics with many absurdly huge numbers of particles: when you limit a system to even just a thousand particles, thermodynamics doesn't work the same and you need to use statistical physics instead. The reverse is true, though: while statistical physics is useful at very small scales, and is mathematically consistent with thermodynamics, it becomes impractical to use on the scales where thermodynamics applies.
Now notice what is going on here: there is a physical reality that is being described, and it's kind of hard to say that that physical reality isn't "true" isn't "real" or what have you. It is what it is. The concept of "truth" comes into play when describing that reality. So the problem with "truth" isn't whether that which is being described is true, so much as whether the description is true.
Some things are easy to describe, and it is easy for those things to be "true" in an "absolute" sense. If you have a two apples, and you eat one, you will only have one apple left. That's easy to describe and it will always be absolutely true.
Other things are extremely difficult to describe: the human mind, how viruses work, the mechanics of the climate, the economy, and complex systems in general. It isn't unreasonable to conclude that it is impossible to write an absolutely true description of such things merely on the basis that it would take nigh-infinitely many words. Therefore we are stuck using incomplete descriptions in order to judge the truth of things. This is where "relative truth" comes into play: it's possible to have somewhat conflicting but equally valid incomplete descriptions of something.
At this point Gödel's Incompleteness Theorem is relevant. It says something that isn't too different from what I've said above, except that it proves it. Essentially, it says that for any sufficiently complex system, if it is consistent, it cannot be complete, and if it is complete it cannot be proven to be consistent. Another way of saying this is that there must exist statements within that system that CANNOT BE PROVED.
So "truth", per se, isn't entirely relevant: the level of knowledge and understanding that is possible is what matters. With any sufficiently complex system, you're not thinking in terms of truth or falsehood, but in terms of accuracy, in terms of how close does a description correspond to reality. Thus, technically speaking, there is no such thing as "absolute truth", but that does not imply that all truth is somehow "relative" or "subjective" or whatever. Far from it. Reality still exists. Things can be objectively measured and compared. What people say can be compared to reality, and others can judge how much bullshit is involved vs how much truth is involved by comparing words to reality.
) but it's definitely still real in some way.
