What is the difference between Microsoft publisher and Microsoft Excel?

Excel is a spreadsheet application and Publisher is an application that creates brochures, business cards etc. So consequently the differences are immense. But it is possible to insert a picture into Excel, and format the text to make it pretty, as you would do in Publisher.
Excel is a spreadsheet program, for working numbers and calculations etc. and Publisher is a desktop publisher which is for working with text to create documents like magazines and brochures.
Excel is for handling data, while publisher is for making posters, business cards etc.