A blog can be:
What is a hosted blog? A hosted blog is one that is hosted by a blog service where you can start a blog for absolutely free. These services handle all of the details of your blog, so all you have to do is write. The free options with these blog's allow you to setup your blog address under a domain owned by the blog provider. So you blog will have a web address something like joesmith.blogspot.com (is a blogger blog).
Examples of free hosted blogging:
There are many advantages to a hosted blog, they are:
This makes hosted blogging perfect for a casual, personal blog. It may also be a good way to get your feet wet and try it out.
There are some hosted blog services that do charge a fee, such as TypePad.
Most of the large hosted blogging services allow you to take it one step further and use your own domain with their service. Many times this is also free, except for the cost for you to register the domain. This is a really great option, especially if you feel you will be blogging in the long term. If you are even slightly serious about your blogging, you absolutely want your own domain name.The other option for starting a blog is to get your own hosting, and setup the blog software yourself. This has many advantages:
Running the blog software yourself also means you have to have at least a basic idea of how a website works. You will likely need to be able to FTP files back and forth, and download and install updates. Many web hosts are making this option easier and easier all the time, so it can be a very simple task if you choose a host that is accommodating to bloggers.
Examples of free blogging software:
Really you need to decide if you are going to try to be a regular blogger and post quite often and for the long haul, then you for sure want at least your own domain, and maybe even your own web host and blog software setup. If you are just in for fun and some casual posting now and then, and you really don't want to worry about any of the details, then a hosted blog service is probably for you.
Whether intentional or not, many folks may take your blog more seriously if you do have your own domain name, it shows that you at least appear committed to the blog. This may in-turn make it easier for you to get links to your blog, which thus increases your blog popularity and traffic.
Also note that what we have covered here is traditional blogging, no where does it say you have to use any official "blog" software. A simple html document can work for you if that is how you wish to do it.