It often means people (usually exploited) who receive work to carry out in their home. A typical type would be textile or craft workers who are paid for piecework that is dropped off to and collected from their home by exploiters.
A friend in Warsaw did this; he used to solder thousands of electronic components in his home and received a few groszy for each. In the end he figured out that the money he received didn't cover the cost of having a lightbulb on to see what he was doing or the heating on to stay warm when he was doing it. He packed it in and found a proper job.