Some basic questions - Java

Hello! I'm new to Java, so I thought I might receive some help here.

I saw this code before, but without any explanation;

Java Code:

public interface Printable {

        public abstract void print();

}

Could someone just kindly explain what it does?

My second questions is related to this code;

Java Code:

public class SystemException extends Exception {

        private String context;

        public SystemException(String message) {

                super(message);
        }

        public SystemException(String message, String context) {

                super(message);
                this.context = context;
        }

        public String getContext() {

                return context;

        }

Quite frankly, I don't exactly understand what SystemException does, especially in this context. I would really appreciate some help to understand these. Also, please do excuse me if I have done something wrong when writing the codes in here. :)