It sounds as if that app has "crashed." So, first, hold on the icon in that bottom bar until it starts to wiggle. Then, when you see it, press on the red minus sign in the upper left corner. The app should disappear from the bottom bar (you're not deleting it - just fully closing it).
Then, do one (or both!) of these two things, restart and reset, to see if it makes the iPad/app "behave" better. To do:
Restart: Hold down the power button until the power off slider appears. Slide it off. When the iPad finishes shutting down, hold down the power button again until the Apple logo appears.
Reset: Hold both the power and home buttons until the screen goes dark and the Apple logo then appears (the slide to unlock screen may or may not appear). Once the logo appears, release the buttons. After a time, your homescreen will appear. Please note that it may take some time for the Apple logo to appear or for your homescreen to appear (or both). This is normal. Eventually, the homescreen will appear.
Hopefully, this should fix your issue and your app will run fine. If not, holler back and we'll try to figure things out. Good luck.
Marilyn