Private – Visible only in its own class

Public – Visible to any other code accessing the class

Protected – Visible only to classes parent(s) and classes that extend the current class

This is important for any developer to know because it shows an understanding that building applications is more than just being able to write code. One must also have an understanding about privileges and accessibility of that code. There are times protected variables or methods are extremely important, and an understanding of scope is needed to protect the integrity of the data in your application along with provide a clear path through the code.