double click (an icon)

When you're using a computer, you "click" links, buttons, and icons to make things happen. Sometimes you need to click something twice to make it work. This is called "double clicking".

Double click the orange and blue icon on your desktop.

an icon

On a computer, an "icon" is a graphic that represents a software program or action. You probably have several icons on your computer's desktop, for example.

"Icons" are different from "thumbnails", which are small previews of what something looks like. For example, if you have a photo saved on your computer, you might be able to see a thumbnail of the photo in some areas of the file system. In other areas, you may only see an icon which shows that it's an image file.

launch (a computer program)

"Launching" a computer program means starting it up. For example:

I tried launching Internet Explorer, but it crashed.

English speakers especially use the word "launch" for programs that start up slowly. The word "open" can be used for any program, whether it's fast or slow to start:

Open Excle, and then choose "File" and then "Create from Template".