The word 'blog' evolved from the term web-log, which represents the notion of online journals/diaries/discussion/records of dialogue. It can be quite useful to set up a blog to either encourage dialogue between students and/or staff, or for group work, particularly when face to face meetings might not be possible. A blog allows students to communicate with other people or to record a personal diary. Blogs can be set up to facilitate comments from other people, helping to progress dialogue between people.
Here is a useful short YouTube video about blogs.
The main differences between a blog and a wiki are that the blog entry is an individual one and thus produces a separate page for every blog entry made, whereas wiki output is collaborative and represents a page that might have been worked on by a number of people.
The word 'Wiki' in the context of the internet denotes a collection of web pages that can be produced collaboratively. A wiki is an ideal platform for group work, especially if learners are unable to meet with fellow group members face to face. These meetings can occur online, and a wiki represents the collaborative effort of the group. A lecturer is able to access the wiki as and when appropriate, and provide feedback throughout.
Here is a useful short YouTube video about wikis.