Can’t run a Jar File

Hey guys,
I downloaded a jar file a few days ago and if i click on the file just nothing happens. I didn’t know what to do, so I searched in Google how to open a jar file. I looked at some pages and ended up with typing commands in my console. This was too complex for me and I didn’t knew if this will solve the “problem”, so I am now asking what I am doing wrong, or what I have to do.