Many people know how to use Views, but not many people know how to extend it properly! This is even more important now that Views is in core for D8. We especially want to discourage people from using views_php to embed PHP in their database, when it's possible to 

I'll cover:

• Views field handlers, to display extra data
• Views filter handlers, to keep only the rows you want
• Views contextual filters (aka "arguments"), to provide filter settings at runtime
• Exposed filters, so that users can change the filter values
• Views relationships, to pull in related data
• Display Extenders, to add a configuration setting to all views
• Porting plugins to D8