Blogs: A Blog page works just like a blog on your website. Once you have created the page in your space simply view it, add a new post, and write. Once it is saved the blog page will keep a running of the blog title and the first line. Your space participants can then click on the title to read the full blog.
Forum: Forum pages allow your course participants or space members to post questions and engage with each other similar to say a Facebook group. But it is housed within your space/membership site/course.
They can click write a post just like you would when creating a blog post and be prompted to add a title and body. Once published members are able to comment.
When participants comment on a forum post they have a WYSIWYG editor that allows them to format their posts and upload images as part of their comments.