How do OpenGL's buffers work?

I don't understood how do OpenGL's buffers work. I learn OpenGL, by means of OpenGL Redbook 8th edition. For example, I have an array of position, an array of color and an array of indices:

static const GLfloat strip_position[] =
    {
        -4.0f,  0.0f, -1.0f, 1.0f,  //0
        -3.5f, -1.0f, -1.0f, 1.0f,  //1
        -3.0f,  0.0f, -1.0f, 1.0f,  //2
        -2.5f, -1.0f, -1.0f, 1.0f,  //3
        -2.0f,  0.0f, -1.0f, 1.0f,  //4
        -1.5f, -1.0f, -1.0f, 1.0f,  //5
        -1.0f,  0.0f, -1.0f, 1.0f,  //6
        -0.5f, -1.0f, -1.0f, 1.0f,  //7
         0.0f,  0.0f, -1.0f, 1.0f   //8
    };
static const GLfloat strip_colors[] =
    {
        1.0f, 1.0f, 1.0f, 1.0f,
        1.0f, 1.0f, 0.0f, 1.0f,
        1.0f, 0.0f, 1.0f, 1.0f,
        1.0f, 0.0f, 0.0f, 1.0f,
        0.0f, 1.0f, 1.0f, 1.0f,
        0.0f, 1.0f, 0.0f, 1.0f,
        0.0f, 0.0f, 1.0f, 1.0f,
        1.0f, 0.0f, 1.0f, 1.0f,
        1.0f, 1.0f, 0.0f, 1.0f,
    };

static const GLushort strip_indices[] =
{
    0, 1, 2, 3, 4, 5, 6, 7, 8
};

Good.Then I create Vertex Array Object is follows:

    GLuint vao[1]; // vertex array object
    glGenVertexArrays(1, vao);
    glBindVertexArray(vao[0]);

In my understanding, first parameter (GLsizei n) is number of an arrays of position(or coordinate of vertices of ONE my object). Then I create Element Array Buffer is follows:

GLuint ebo[1]; // element buffer object
glGenBuffers(1, ebo);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo[0]);
glBufferData(
             GL_ELEMENT_ARRAY_BUFFER, 
             sizeof(strip_indices), 
             strip_indices, 
             GL_STATIC_DRAW
);

Then I create Vertex Buffer Object is follows:

GLuint vbo[1]; // vertex buffer object
glGenBuffers(1, vbo);
    glBindBuffer(GL_ARRAY_BUFFER, vbo[0]);
    glBufferData(
                 GL_ARRAY_BUFFER, 
                 sizeof(strip_position) + sizeof(strip_colors), 
                 NULL, 
                 GL_STATIC_DRAW
    );
    glBufferSubData(
                    GL_ARRAY_BUFFER, 
                    0,                      //offset
                    sizeof(strip_position), //size date
                    strip_position          //data
    );
    glBufferSubData(
                    GL_ARRAY_BUFFER, 
                    sizeof(strip_position), //offset
                    sizeof(strip_colors),   //size data
                    strip_colors               //data
    );

Next I call glVertexAttribPointer() is follows:

glVertexAttribPointer(
                      0,         //index
                      4,         //size
                      GL_FLOAT,  //type
                      GL_FALSE,  //normalized
                      0,         //stride
                      NULL       //pointer
);
glVertexAttribPointer(
                      1, 
                      4, 
                      GL_FLOAT, 
                      GL_FALSE, 
                      0, 
                      (const GLvoid*)sizeof(strip_position)
);
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);

What does that function?(glVertexAttribPointer() and glEnableVertexAttribArray())
Okay. I finished initialize a my data. Now I can draw it's follows:

glBindVertexArray(vao[0]);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo[0]);
glDrawElements(GL_TRIANGLE_STRIP, 8, GL_UNSIGNED_SHORT, NULL);

How OpenGL understood, which buffer need to use and where it is? Word "bind" is mean a relation? i.e. something bind with something? And If I want to display a two object, what do I do? For example, I have a two arrays of position, a two arrays of position and a two arrays of indices?

static const GLfloat TWOstrip_colors[] =
{
    1.0f, 1.0f, 1.0f, 1.0f,
    1.0f, 1.0f, 0.0f, 1.0f,
    1.0f, 0.0f, 1.0f, 1.0f,
    1.0f, 0.0f, 0.0f, 1.0f,
    0.0f, 1.0f, 1.0f, 1.0f,
    0.0f, 1.0f, 0.0f, 1.0f,
    0.0f, 0.0f, 1.0f, 1.0f,
    1.0f, 0.0f, 1.0f, 1.0f,
    1.0f, 1.0f, 0.0f, 1.0f
};
static const GLfloat TWOstrip_colors[] =
    {
        1.0f, 1.0f, 1.0f, 1.0f,
        1.0f, 1.0f, 0.0f, 1.0f,
        1.0f, 0.0f, 1.0f, 1.0f,
        1.0f, 0.0f, 0.0f, 1.0f,
        0.0f, 1.0f, 1.0f, 1.0f,
        0.0f, 1.0f, 0.0f, 1.0f,
        0.0f, 0.0f, 1.0f, 1.0f,
        1.0f, 0.0f, 1.0f, 1.0f,
        1.0f, 1.0f, 0.0f, 1.0f,
    };

static const GLushort TWOstrip_indices[] =
{
    0, 1, 2, 3, 4, 5, 6, 7, 8
};

How do this?