Pagination is the process of separating print or digital content into discrete pages.
For print documents and some online content, pagination also refers to the automated process of adding consecutive numbers to identify the sequential order of pages. Some types of website content benefit from being broken into separate pages to make them more user-friendly, such as search engine results pages (SERP), blogs and discussion forums.
Online articles are sometimes paginated to break up content. There is some justification to organizing long articles into multiple pages to aid the reader. However, even relatively brief articles are often paginated so that a page consists of a single paragraph and a visitor might have to click through ten or more pages to read the complete text. The purpose is to increase page views and, as a result, ad impressions -- the number of times that a website visitor sees a given ad. However, because most readers don't complete multi-page articles, the presentation of multiple short pages rather than a single long one may actually result in fewer ad impressions.
See a Google video about pagination and search engine optimization (SEO):