In order to understand the difference between static and dynamic binding in Java, it's important to first learn what is binding? Binding means the link between reference and actual code e.g. when you refer a variable it's bonded to the code where it is defined, similarly when you call a method, it's linked to the code where a method is defined. There are two types of method binding in Java, static binding and dynamic binding. When a method is called in Java it's bonded to the actual code either at compile time or runtime, when the program is actually started and objects are created. As the name suggest, static binding is more of static nature hence it occurs at compile time i.e. your code knows which method to call once you compiled your Java source file into a class file. Since it happens early in program's life cycle it is also known as early binding in Java.
The "illegal start of expression" error is a compile time error when the compiler finds an inappropriate statement in the code. The java compiler, javac, compiles your source code from top to bottom, left to right and when it sees something inappropriate at the start of an expression, it throws "illegal start of expression" error. The most common reason of this is a missing semi-colon. You might know that every statement in Java ends with a semicolon, but if you forget one, you won't get an error that there is a missing semi-colon at the end of statement because the compiler doesn't know the end. When compiler checks the next statement it sees illegal start because an earlier statement was not terminated. The bad part is that you can get tens of "illegal start of expression" error by just omitting a single semi-colon or missing braces, as shown in the following example.