Basically debugging is a process of finding and rectifying the bugs or defects of a computer program or a piece of electronic hardware.
When you debug a program then first you need to start with a problem, isolate the source of the problem, and finally fix it.
A debugged program means that all the bugs have been removed from the program or you can say that the program is free from errors.
Browser sniffing is a process of detecting the information related to a browser such as name, version, operating system and type of the browser.
Browser sniffing also detects the runtime environment of the browser in which a web page is executed.