A stay on a judge's decision is basically a "hold". The decision cannot be used as a basis for any action. In other words, although she ruled that it was unconstitutional, her decision didn't go into immediate effect as long as the stay was in place. This meant that same-sex marriages could not be performed based on her decision. Once the stay is lifted, the decision goes into effect and same-sex marriages can be performed within the area affected by her decision. In this case it is Miami-Dade County, Florida.