How would you respond if asked that question in those words? It is impossible to even guess with so little information.
What version of Photoshop?
What operating system?
Has Photoshop ever worked?
Can you tie this issue with something else you have done on the computer?
Have you tried basic steps like restarting your computer?
Has Photoshop been open previously and not closed properly?
Is there a dialog window awaiting input, and hidden behind other windows?