What is a blog? A blog is a way to share information with everyone on the internet. There are a limited number of people that can edit a blog. Anyone can view it, but only the author can edit it. Sometimes a small group creates a blog, or there can be a large number of authors creating posts on one blog, called multi-author blogs (MABs). Blogs are used to share opinions or inform people on topics, and ask for opinions from others.
What is a wiki? A wiki, like a blog, is a way to share information with everyone on the internet. But where a wiki is different, anyone can edit or add information to a wiki. Sometimes wikis are used in business for collaboration projects, where a large amount of people need to contribute to a project.
Wikis are very easy to edit, they don't require any special software or browser add-ons to edit them. Wikis also have history pages, where you can view the changes/edits other people have made. Just because anyone can edit or add to a wiki, does not mean the information from wikis are bad, Wikipedia is a good resource for a lot of information. But don't let wikis be the only place you find information, use other more reliable sources, in addition to wikis, when gathering information about a topic your are researching.
