Keywords are specific terms that serve as a code's key. Because they are Java's predefined terms, they can't be used as identifiers. In Java, identifiers are symbolic names that are used to identify objects. They can be anything from a class name to a variable name to a method name to a package name to a constant name.
When naming identifiers, there are several guidelines to follow: the identifier's initial character must be a letter of the alphabet (upper or lowercase) or an underscore ('_'). Letters (upper or lowercase), underscores ('_'), or numerals can make up the rest of the identification name (0-9).
Only alphabetical characters make up a keyword. Alphabetic letters, numerals, and underscores can all be used as identifiers. Keywords include int, char, if, while, do, class, and so on. Test, count1, high speed, and other identifiers are examples.
Keywords are the words and phrases that people use to find what they're looking for in search engines. For instance, if you wanted to buy a new jacket, you might search for "mens leather jacket" on Google. That phrase is still a keyword, despite the fact that it contains more than one word.
For instance: double accountBalance; int money; Money and accountBalance are identifiers in this case. Also, keep in mind that identifier names must be distinct from keyword names.