You can use this phrase to describe how well you understand something. It's an intelligent-sounding phrase. In the situation above, you could also say:

I don't know much about Korean politics.

But this version doesn't make you sound as intelligent as the original version.

Other adjectives that you can use with "have a ___ understanding of ___" include:

She'll probably have a better understanding of what's going on.

We now have a deeper understanding of the ecological effects of greenhouse gasses.

We want to make sure that all students have a basic understanding of Algebra.