Blogs vs. Wikis

Creation / Ownership:
Blogs are generally created by one or selected people to publish or post an online journal in a chronological form. The control of the contents remain in the hands of a few creators. Wikis are generally created by a group of users to publish or post as a website in no specific form. In fact, Wikis present a decentralized control in a community setting (class reading).

Collaboration / Editing:
Editing a post in a blog is usually reserved by the post's creator. Other owners of the blog are able to comment on the article or publish a completely a new topic for others to comment. Wikis, on the other hand, are a free form medium and the entries can be edited by anyone in the user group in any form.

Creativity / Content:
Blogs are usually about a personal opinion or observation or a topic of discussion. The contents are therefore more individualistic (YouTube Video: Blogs in Plain English). Wikis are about creating a shared knowledge database i.e. highly public content (YouTube Video: Wikis in Plain English).

Communication:
Blogs are a means to communicate one opinion, disclosure or event at a time. Hence the process of communication is concise, slow and rigid. However, Wikis allow collaboration and communication from all sources making the flow of information detailed, fast and flexible.

Purpose:
Blogs are considered an alternate to webpages which require knowledge of special codes and design sense (Communication and Collaboration on the Internet: Blogs, Wikis, ...). It is also a fast and easy way to communicate from an individual view point. For example, the birth of a child in the family or the home team winning the local school championship etc.
Wiki on the other hand is a website that brings in streams of information on a single topic to form a pool of information which can be enhanced by anyone in the community. For example, information on the Moon can be started and updated by anyone on a single page.