Does it get erased completely

So I am wondering...I have a file that I want to completely obliterate/destroy. Can I handle that one file at any moment or must I do a complete system cleaning. If I send it to trash does it wipe itself out or does it wait there until I run the program. For example a picture or a text that I want immediately destroyed/ obliterated etc. How can i do it without running the whole program which takes a ton of time? Thans in advance for any answers or explanations.... Billy