The Korean whaubica that Poland will buy. What's a K9?

The heated discussion is caused by the Polish Ministry of Defence's planned acquisition of the Korean self-propelled cannonohaubic K9, which is partially the protoplast of our Krab. Regardless of the discussion on the rightness of its broad introduction in the situation erstwhile Poland produces Kraba (with a K9) chassis, it is worth answering the questions about what this plan is, what is its past and how can it look like in the future?