A blog is a website published on the Internet consisting of discrete, often informal diary-style text entries (“posts”). Posts are typically displayed in reverse chronological order, so that the most recent post appears first, at the top of the web page.

Many blogs provide commentary on a particular subject or topic, ranging from politics to sports. Others function as more personal online diaries, and others function more as online brand advertising of a particular individual or company.

A typical blog combines text, digital images, and links to other blogs, web pages, and other media related to its topic. The ability of readers to leave comments in an interactive format is an important contribution to the popularity of many blogs. However, blog owners or authors need to moderate and filter online comments to remove hate speech or other offensive content. Most blogs are primarily textual, although some focus on art (art blogs), photographs (photoblogs), videos (video blogs or “vlogs”), music (MP3 blogs), and audio (podcasts).

History of Blogs
The term blog comes from the expression weblog, which was an early term used for the format. Blog can also be used as a verb, meaning to maintain or add content to a blog.

Until 2009, blogs were usually the work of a single individual[citation needed], occasionally of a small group, and often covered a single subject or topic. In the 2010s, “multi-author blogs” (MABs) have developed, with posts written by large numbers of authors and sometimes professionally edited. MABs from newspapers, other media outlets, universities, think tanks, advocacy groups, and similar institutions account for an increasing quantity of blog traffic. The rise of Twitter and other “microblogging” systems helps integrate MABs and single-author blogs into the news media.

The emergence and growth of blogs in the late 1990s coincided with the advent of web publishing tools that facilitated the posting of content by non-technical users who did not have much experience with HTML or computer programming. Previously, a knowledge of such technologies as HTML and File Transfer Protocol (FTP) had been required to publish content on the Web, and as such, early Web users tended to be hackers and computer enthusiasts. In the 2010s, majority are interactive Web 2.0 websites, allowing visitors to leave online comments and even message each other via GUI widgets on the blogs, and it is this interactivity that distinguishes them from other static websites. In that sense, blogging can be seen as a form of social networking service. Indeed, bloggers do not only produce content to post on their blogs, but also build social relations with their readers and other bloggers. However, there are high-readership blogs which do not allow comments.

How many blogs are there?
As of February 2011, there were over 156 million public blogs in existence. As of February 2014, there were more than 300 million blogs, including 172 million Tumblr and 75.8 million WordPress blogs worldwide.

Blogger is the most popular blogging service used worldwide. Technorati has 1.3 million blogs as of February 2014.