The getKey command return the key code of the last key that was pressed, or zero if no key was recently pressed. Here are the values that getKey returns for each keypress:
A loop like this wait until any key is pressed and then exits.
After this, you can perform some action based on the value of the keypress. By using K=105, the Repeat loop only exits when the last key pressed was [ENTER].
You should post questions in the same thread if they are all related to your progress learning TI-BASIC so that it is easy to refer to later. If you have a question about a specific project or a different subject, it would be appropriate to create a new thread. Generally, you should "Reply" to comments regarding the same question, and ask a new question about the same subject by creating a "New Post" in the same thread.