What does it mean to unzip a file in a computer?
It's kinda like unzipping jeans but I don't want to get more into that so unzipping a file without Winrar or any unzipping program will just open the file, except you have to extract it to make use of it's .exe files and other stuff.
Open i guess
In computer, to unzip a file is to open it. When a file is zipped, it means that it is condensed to carry a number of files, thus to read each file individually, you need to open/unzip it.