JAVA is a general purpose high level programming language. General purpose means using JAVA we can develop varieties of applications like desktop application, web application, enterprise application, device application etc. and high level programming means the source code whatever you are writing that is in human readable form.
JAVA is a Technology, because JAVA having huge library support for simplifying the code complexity. Due to support of readymade methods JAVA program is very easy.
JAVA is an OOP Language, because JAVA supports Object-Oriented Programming(OOP) features like Class, Object, Data Abstraction & Encapsulation, Inheritance, Polymorphism, Dynamic Binding, Message Passing etc. Another fact is a JAVA program is nothing but a class. Here everything is a class. That means a JAVA program consisting one or more than one class, which also represents OOP.
JAVA is a Platform. A Platform is an environment (hardware and software) where we can execute our java program. Java having it's own JRE(Java Runtime Environment) thats why we can say java is itself a platform.
Download Java from the official Java web site: https://www.oracle.com