Why can Java code be ran on multiple operating systems without modifying the code? (For example on Windows and MAC OSX)
Java runs code in a JVM. (Java Virtual Machine). As long as a device has a JVM it can run and execute Java code.
Is HTML a programming language?
No, It is a markup language. HTML is a formatting language. It is used to tell how things should be laid out. HTML is not turning complete and cannot preform calculations.
Is C++ a compiled or interpreted language?
C++ is a compiled language. That means that C++ code must be converted into a language that the computer can understand. To do this C++ is sent through a compiler. The compiler converts the C++ code into machine "code" that the computer understands and can run.