A blog post is be to be heard, or to speak so that someone might listen, or just to get it out.
An essay is either because someone assigned it or because brevity overruled.
A manifesto is to declare something and embolden a movement.
A memo is so coworkers stop leaving the lights on.
A memoir is to immortalize memories before they fade. It can lay a foundation for empathy.
A novel is to let others into explore an imagined world.
A press release is for attention.
A product review is for a paycheck.
A scrawling in cement is to leave a mark.
The author’s motive should always be questioned.