PRL- the shortcut of Polska Rzeczpospolita Ludowa (The Polish People's Republic) which lasted from 1952 to 1989. This period is called "komuna" by polish people. In 1989 there took place (almost) democratic elections which was was the first step to free Poland.
In that time happened many dramatic occurrences, shops didn't have products and if you had wanted to buy something, you would have had to stay in pretty long queue. It was hard period for Poles, but thank god, now we're free and still in economic progress. ^^