Interface vs abstract class in Java C#

See http://studycoding.org for all tutorials by Shad Sluiter. Interface vs abstract class. What is the difference between an abstract class and an interface? When to use an interface? When to use an abstract class? java interface. Are interfaces better than abstract classes? Is an abstract class better than an interface? How to create a database app in Microsoft Access https://www.youtube.com/watch?v=aV1XLxEcxaQ How to create a database web app in PHP and mySQL https://www.youtube.com/watch?v=yAmXgDKu2go&list=PLhPyEFL5u-i0zEaDF0IPLYvm8zOKnz70r How to create a database web app in C# https://www.youtube.com/watch?v=m8IuIoAlciM&list=PLhPyEFL5u-i2ShGqmuP3uDdSy06hzBzdo