Thanks for reply
Now I think I kinda get what video modes are, but I'm still confused with Windowed Fullscreen.
According to "Windowed full screen" guide, it says
const GLFWvidmode* mode = glfwGetVideoMode(monitor);
GLFWwindow* window = glfwCreateWindow(mode->width, mode->height, "My Title", monitor, NULL);
If I create window like this, I get Fullscreen. Window gets minimized when focus is lost. If I disable GLFW_AUTO_ICONIFY, it seems like Windowed Fullscreen but the window always stays on highest level (can't be overlapped or topped by other windows), which is not what Windowed Fullscreen should be.
I guess it's obvious because monitor is not NULL, which means it's "Fullscreen" not "Windowed", but if I set monitor to NULL, then I get fullscreen-sized decorated window(bordered with title). I have to set GLFW_DECORATED to false in order to make it Windowed Fullscreen like I posted earlier.
So is the guide above wrong or am I? I think I'm overthinking with Windowed Fullscreen, but really want to know thoroughly.