9. What is texture unit?

• Texture unit is a piece of hardware that has access to a texture image

• The glActiveTexture() function

  
      const int TEXTURE_UNIT_ZERO = 0;
      // Turn on texture unit 0:
      glActiveTexture( GL_TEXTURE0 + TEXTURE_UNIT_ZERO );
  
  

  changes the current texture unit.

• All subsequent texture operations (glBindTexture(), glTexImage2D(), glTexParameterf(), etc.) manipulate the texture bound to the current texture unit.