the frame changes the colour

You think you know stuff but that's just an impression you have. You realise how little you know when you try to use your knowledge. I'm learning C++ again for the first time in a while, and instead of just following the tutorials, I know enough to see where the instructor is going and then do it myself. It's then that I appreciate how much and how little I know - both how much and how little I know. 

I know enough to have a go at doing the thing, but not enough to get it right. But then I know enough to understand the error message and make the changes I think are required, but not enough to get the program to work. So then I watch more of the tutorial and learn. I also try to do things that aren't covered in the tutorial I'm watching. I'm working up to the point where I'll be able to start working on projects - making a game or a website or an app. 

When I first started learning about C++ I followed the tutorials and did what they said, but I didn't understand a lot of it. Then, in successive rounds of different tutorial series', I understood more and more. When I first started learning HTML and CSS, my big problem was that I didn't know where to write the code. I read a book about HTML and CSS and it told me a lot about what happens when you enter different code...but where? How do you bring up that screen or whatever it is where you enter the code? And what is the screen that shows the results. I didn't know the basic mechanics of it. To solve this, I turned to youtube. I honestly feel like watching youtube tutorials and doing what they show you, is the best way of learning these things. 

So, as I said, you think you know something or know about something, or you might think you don't know about something, but the reality is different to your impression. The line between knowing and not knowing is not so fine. Sometimes, when you think you don't know something, it's better to say you do, and sometimes, when you think you do know something, it's better to say you don't.