Vico is a modal editor. This means there are different modes in which you interact with the editor. The most fundamental modes are the insert mode and normal mode. Regular keys pressed while in insert mode causes text to be inserted. In contrast, while in normal mode, regular keys are attached to editing commands such as delete, change or copy text.
If you have used the vi or vim text editors, you should feel comfortable with Vico. If this is your first encounter with a modal editor, you might feel a bit overwhelmed at first. But if you give it some time and learn the basics, you'll be rewarded with a highly efficient text editing tool.