A word processor is a computer program used for writing, editing, and formatting text documents. It allows users to format text with features like changing font size and style, alignment, and adding images. Spell checkers compare words to an internal dictionary to find spelling errors, while grammar checkers highlight sentences with grammatical issues. Word processors enable creating standard documents like letters by using templates and mail merge to insert recipient details from a database. Other features include word wrap, search and replace, tabs, and tables.