https://en.wikipedia.org/wiki/Single_Table_Inheritance
https://martinfowler.com/eaaCatalog/singleTableInheritance.html
From the wikipedia page:
Single table inheritance is a way to emulate object-oriented inheritance in a relational database.
All fields of all the classes are stored in the same table, hence the name "Single Table Inheritance"
This will result in potentially a lot of Null cells if there is not a lot of inherited (shared) properties of your objects.
This is used in object-oriented programming and is seen in frameworks like Ruby on Rails, in Ruby, and in Java in various ORM solutions.