system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is String Theory? Has it been proved wrong? Whats the current replacement theory/idea?
gpt
There are four fundamental forces in the universe, gravity, the electromagnetic force, the strong force, and the weak force.   We can describe so of these forces with two models, general relativity can be used to explain gravity, while the standard model explains the three remaining forces.  These theories are immensely successful, however they are both incomplete, and we would like to have one theory which explains all for forces. 

 Actually combining these forces turns out to be really difficult.  For one thing, gravity is incredibly weak compared to the other forces and we have no clue why.  Another problem is that if we attempt to describe gravity using the same math as we do for the other three forces we end up with a theory which isn't predictive.  We want theories to be able to make predictions, so if a theory isn't predictive this is a pretty big problem.   

String theory is one way of having a theory which explains all four forces.   However, it's incredibly mathematically complex, and so far we don't have any way to test it using current technologies.