What does it mean when your feet swell?

I'm a 31 year old female and lately my feet have been swelling. It happens mostly at night (i work 3rd shift) and I have no pertinent medical history. I hear of this happening in elderly people but it seems weird that its happening at my age. What could this be??What does it mean when your feet swell?
I'd say edema--but I'm no doctor, that can probably be relieved by elevating your legs for 45-60 mins. Also, if you stand for extended periods of time (at work/school) swelling is common. Your body could also be retaining fluid. Best to check with your doctor. The swelling could be something a little as standing for long periods of time or as serious as a sign of congestive heart failure. Since heart attacks are quite common with women, I'd definitely check with a doctor.
you're gettin' fat. ahah. or atleast in my situation that's what it means...!
Being on your feet for long periods can make feet swell. Also, you might be retaining water. When the weather gets warmer for me, my ankles swell. Drink lots of water to try to flush the water out. Congestive heart failure can cause swelling too in the elderly.
I had this happening for a few weeks. Went to the doctor for it. My swelling was also in my calfs along with my feet. He said to lay off the salt and exercise. The ONE thing he did stress was, that it goes away at night when I go to bed. It did. And all day during the day, they would swell again. He never said what it could be if it didn't go away when sleeping, but I sensed it would be serious if not. He wanted to see me right away if it didn't go away when sleeping. Hope this little bit helps.
It's nature's way of telling you to sit down.