A search engine's job is to index important information and to display this information when a user requests it. When Google crawls a website, it develops an idea of what that website is about and decides where and how to add the site to the Google index.
As you can imagine, the text content on your website is one of the most important factors Google analyzes to learn what your website is about and how it should be indexed. For this reason, copying text content from another website—especially a competitor's website—can cause serious problems.