The major difference between Word and Publisher is that Word can be used for creating documents, legal letters, blogs, articles, CVs, etc. However, when we talk about a Publisher file, it is used for creating flyers, catalogs, newsletters, greeting cards, wedding cards, and other similar pages.
Word software is generally used for text processing, while Publisher software emphasizes page layouts. So, when you want to write a simple letter, you can use a word document and not a publisher, but when you have to design flyers, it's good to use a publisher instead of a word document.