The clutch hydraulics have failed. You'll need to get it taken to a garage to get it sorted, unless you can DIY?
Why haven't you pulled it out of gear so you can move it about?
Is the car parked on a slope? If so then the weight of the car will be loading the gearbox and it will be a lot harder to get it out of gear. It can usually still be done with brute force but the better way is to take the load off the gearbox by pushing the car back up the slope. Depending on the amount of hill, this takes several burly friends and a light-weight child (just large enough to reach the brake, strong enough to get it out of gear and reliable enough so that the car doesn't roll back over your friends). Alternatively, if you can get a tow rope on to it, pull it uphill using another vehicle while you are in the car to put pressure on the gear stick.