What is a Blog?
This is a blog. The term come from the phrase "web log", which refers to an online log of any type of writing of information, thoughts, feelings or general content. It is usually informal and created and maintained by individuals or small groups with a particular focus of interest. Blogging 'platforms' are software installations which make it easy for any user to create, edit and publish a blog. This platform, ( the one you're reading now,) Blogger, is now owned and run by Google.
What is a Wiki?:
A "Wiki" is also a website, run on a publishing platform, similar to a blog, which is generally informational, and can be edited by any user. The best known is the site Wikipedia which has become one of the largest sites in the world. The wiki, unlike the blog, can be edited by any user, not just the original publisher.
Wikis are very easy to create, just like a blog. They can be very useful in group collaboration but this can also turn counter-productive as more contributors join in the mix. The ease of editing the wiki can lead to inaccurate and negative info being posted and derailing the main purpose of the effort.
Wikipedia can be edited by any user instantly, without even registering as a user. Each visitor's IP address is collected with these edits to identify the source. This extreme openness would seem to be asking for trouble, but the stats from Wikipedia report that 82% of edits come from registered users and 18% from unidentified users (IP address only). Erroneous posts are usually corrected very quickly.
After some study and research into wikis, including the
Wikipedia founder's TED Talk, I have come to a new appreciation of the usefulness and integrity of wikis. The fact that users can abuse the privilege in publication of wikis does not seem to be as big a problem as I had expected. I base this on the talk referenced here, and after reviewing sever Wikipedia article on topics I am most familiar with. I find the quality and accuracy is very good. Prior to exploring the topic I had less appreciation for the usefulness of wikis.
Wiki Hosting
It is easy to start your own wiki using sites such as these

PBWiki.com
wikidot.com
wikihost.org
10 Free Wiki Platforms