WSS 2.0 : How to save properties of webpart from webpart code

There are two methods, SaveChanges and SaveProperties provided by WSS which sometimes misleading users. Here I provide details for which method to use and when to use.

SPWebPartCollection.SaveChanges()  - This method is used to save the changes made in the web part from out side the web part code. For e.g., the console application, windows application etc..,

SPWebPartCollection.SaveProperties - This method is used to save the properties within the web part code.