You are a philosopher, right? So, let's see what is that, in my view, of string theory.
Suppose you live in a simulated universe, like in the movie Matrix. You can see the world functioning normally, with its people that looks like made of flesh, blue sky, sun, water, everything perfectly normal. But, ontologically, nothing is like that, in fact, the real world is just electrons propagating in circuits, and nothing more. The experimental realization of the world do not have a geometric ontological part, but an abstract one. Consider here that there is no real world, except for the electrons and circuits.
Strings in the "real world", or base space (as it is called in string theory), are what I would analogically call the circuits with the electrons in the Matrix. They are designed to yield in the simulated universe, the target space, something equal to our daily world, as it is experimentally measured. Well, it happens that they do not yield 4 dimensions, but 10 of them. Note that the strings themselves have a similar string counterpart in the target space, plus other objects with more dimensions called branes. String theorists take advantage of the 6 extra dimensions, these branes and strings, to describe specific particle interactions, specially the non gravitational ones.
You must have heard of 5 string theories. Well, they are the same. But you will find, on papers, several very different classes of physical models, linked to specifically each of them. Don't worry, it is like using 5 different circuits to compute the same thing. It is just that it is almost infinitely easier, optimized to describe a situation with one circuit than with another. Like using graphics card to boost the performance of a game.