Waterfall is divided into blogs, which is what you put your content on. They work a little differently to other sites, with fewer restrictions.
An account can have as many blogs under it as you like. Each of these blogs has access to the full range of features with no limitations, with the exception of group blogs - if you're not the owner of the blog and only a member, you can't set it as your main blog. The owner of the blog doesn't have this restriction.
Separation of Blogs
Each blog maintains its own follows and likes.
This means that, for example, you can have a personal blog that you follow your friends on, and a fandom blog that you follow blogs posting about your favourite show on. Depending which blog is active, any likes, follows, or comments will be sent from that blog. Additionally, you can send asks from these blogs.
This removes the distinction of "sideblogs" somewhat, as any blog can be used for any purpose.
As you switch between blogs, your dashboard will change to reflect the blogs you follow from that blog, unless you have the OmniDash option enabled.
Switching your main blog
Your "main blog" has no real bearing on site functionality, and serves only as which blog is made automatically active when you first log in on a new device. If you'd like to switch your main blog, you can do so in your user settings.
Marking Blogs as Adult Only
Blogs can be marked as adult only in the Blog Settings using the appropriate checkbox. This can be done by users over the age of 18, and will block minors from viewing your blog. If the content you post is mostly adult or NSFW, this is mandatory in addition to the appropriate tags, and should be done as soon as possible.