When a program is running on a computer the processor is constantly performing very many, very tiny electronic operations. For example, one such operation reads one byte of data from main memory into the processor. Another operation tests if one of the bits in the byte is a "1" bit. Most processors are able to perform several hundred types of small operations like these.
Those are the only things that a processor can do. It has a small set of tiny electronic operations that it can to perform, and that is all. These little electronic operations are performed one at a time. But millions of them are performed per second. Millions of small operations can add up to a large and useful action.
Everything that a processor does is built out of these tiny operations! Luckily, you don't need to know these details to write programs in Java. The purpose of a "high-level language" like Java is to organize the tiny electronic operations into large, useful units represented by program statements.
(Thought question:) When you click on a hyperlink (such as the next button) your Web browser (a computer program) finds and displays a new page. About how many detailed electronic operations does the processor perform in doing this?