Difference between LaTeX classes and packages

Hi guys,

• The first thing to remember is that a document uses only one class, but it can use many packages. 
• That means that particular class we use in our document (e.g. myclass.cls) sets the overall format, like the structure of the sections and etc.
• A package, however, add more functionality to the document. For example tikz is a package which allows you to draw diagrams, but does not modify the document style at all.
• A class file can also be based on another "one" class and multiple packages.