In theory, an IQ test is supposed to measure your "potential for learning". The idea is to separate knowledge from the ability to learn something/problem solve, so that ignorance doesn't change the results. In reality this is can't be done perfectly and you can absolutely get better results on an IQ test by practicing. But this means that people who already have gained some of the same skills that would be honed by practicing for the IQ test will score better than someone who has not gained those skills.

So IQ tests are intended to measure something that you shouldn't be able to change, but fail to do so perfectly, and so it is NOT always the same. But the true value of the thing that IQ is a proxy for shouldn't be able to be changed.