What is a wordprocesser and its function?

A Word processor is a computer application that helps with writing down Words (usually into documents, letters or notes etc). Typically a Word processor will help with:
1. Creating a new letter or document (potentially from a template).
2. Editing and changing a document (searching for text, changing text, moving text etc)
3. Viewing of documents, printing of documents and saving of documents for later retrieval.