What are variables in Java?

In Java, variables are names or identifiers used to store and manipulate data. They can hold different types of data such as integers, floating point numbers, characters, boolean values, etc. Variables are declared with a specific data type in a program, and can be read from or modified after being assigned a value. Naming conventions for variables include starting with a letter, underscore, or dollar sign, and can contain letters, numbers, underscores, or dollar signs. Variables in Java also need to be initialized before use.