Blog is short for Web Log, which is basically an online journal for posting news and other events to your web site. The blog software makes posting and publishing easy while also offering features such as reader comments, automatic archiving, and chronological post order with recent being near the top.
Blogs can be considered the simplest form of a personal home page and are available as either scripts you install on your hosting account (see other hosting types) or as sign-up services which can be standalone or integrated into your existing site with XML or FTP.
You can even blog directly from mobile devices (particularly cell phone with camera) using text, video, and pictures. Snap a picture and email it to a special address and the picture will automatically show up online. This is called a mobile web log or moblog for short.
Popular Blogging Tools and Services
Movable Type - a powerful web publishing application which can be used for blogging or news, has to be installed on a hosting plan. Free and priced versions available.
WordPress - free, feature rich, and easy to use personal blog script which runs on PHP and MYSQL. Requres installation on hosting plan.
blogger - easy to use free service which offers hosting (yourblog.blogspot.com) and options to publish to your own hosting server through FTP or XML.