Many community members have asked what the difference is between a blog post and a forum discussion thread. If you're in doubt about which you should create, the answer is almost certainly a forum thread. For a more detailed explanation, read below:
Forums are used to pose questions, start discussions, give project updates, etc. Generally, if the point of your typing is to elicit a response, to engage in conversation with other community members, a forum thread is your best bet.
Blogs, on the other hand, are more of an online journal or diary. Blog entries should be used to document projects you're working on, or individual steps from your projects in more of a 'STORY' type format. You're putting your story out there for others to read and learn from. You can still use a blog to ask questions or get input, but it shouldn't be the primary purpose. Creating a forum thread is a one-time occurrence, completely separate from the creation of other forum threads, while blog posts are created on a more regular basis (perhaps daily, weekly, etc.) by someone who would consider themselves a 'blogger.'