The Java is a programming language and also a platform too. For better understanding the Java as programming language and Java as a platform, lets first understand platform and programming language.
What is a Platform?
A platform is a major piece of software, as an operating system, an operating environment, or a database, under which various smaller application programs can be designed to run.
A platform denotes a complete software programming execution environment and underlying subsystem with language, runtime componentsand all associated libraries and binaries. The result of using a platform (Java for example) is to run small software applications.
What is a Programming Language?
A programming language is a formal computer language designed to communicate instructions to a machine, particularly a computer. Programming languages can be used to create programs to control the behaviour of a machine or to express algorithms.
A programming language contains a set of library files having pre defined commonly useful features to develop the applications and a compiler tool which can convert the source code(human readable) into machine code(processor readable) by following some specific syntaxes.
The Java is a programming language and a platform too, because we can develop and run the applications using java only and we do not need any third party software to compile or run the java applications.