You write a post at the top of the feed. You can attach pictures, videos and GIFs and decide who may reply.
Videos
Once a video is uploaded you can send the post right away. The server does the processing in the background. Your post appears as soon as the video is ready, and you get a notification. If the processing fails, your text becomes a draft again.
Drafts
If you leave the editor with text in it, it is kept as a draft and you can carry on later.