Clock group vs. clock false path

I have a couple of clocks coming in that are not related to each other. Before I put them in a group, I ran TimeQuest and it was complaining about some setup slack violation. I know I should have used set_clock_groups for these two clocks, but TimeQuest gives me the option of declaring a false path between the two clocks - what is the difference between setting a false path between clocks and putting them in a group?