This is one subject that can get very complex.
1. It depends on if it was deleted from the deletion bin.
2. It depends on how long it has been since you deleted it. If it has been quite some time, you may not be able to get it back. This is because it eventually gets overwritten.
3. It depends on the operating system.
There are numerous other situations that may make it difficult to restore. HOWEVER, the file can be restored in at least some cases. You can buy software that will do this for you. However, there is another way.
I have decided to lead you to a link in this case. I feel it has been well done and I don’t need to reinvent the wheel. Here it is: geekgirls.com