I am just starting to learn OpenGL today from this tutorial: http://openglbook.com/the-book/  
I got to chapter 2, where I draw a triangle, and I understand everything except VAOs (is this acronym OK?). The tutorial has this code: 

    glGenVertexArrays(1, &amp;VaoId);
    glBindVertexArray(VaoId);
While I understand that the code is necessary, I have no clue what it does. Although I never use VaoId past this point (except to destroy it), the code does not function without it. I am assuming this is because it is required to be bound, but I don&#39;t know why. Does this exact code just need to be part of every OpenGL program? The tutorial explains VAOs as:

&gt;A Vertex Array Object (or VAO) is an object that describes how the vertex attributes are stored in a Vertex Buffer Object (or VBO). This means that the VAO is not the actual object storing the vertex data, but the descriptor of the vertex data. Vertex attributes can be described by the glVertexAttribPointer function and its two sister functions glVertexAttribIPointer and glVertexAttribLPointer, the first of which we’ll explore below.

I don&#39;t understand how the VAO describes the vertex attributes. I have not described them in any way. Does it get the information from the glVertexAttribPointer? I guess this must be it. Is the VAO simply a destination for the information from glVertexAttribPointer?

On a side note, is the tutorial I am following acceptable? Is there anything I should watch out for or a better tutorial to follow?

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What are Vertex Array Objects?