To write your status, simply click on the Pencil & Paper icon in the top right (in the Frio theme), or click in the box that says "share" (other themes).
When you do this, the posting dialog box will appear or the share box will expand.
You can see some formatting options such as Bold, Italics and Underline, as well as ways to add links, pictures (dependent on the theme), and a paperclip icon to attach or embed content.
You can use these to upload pictures and files from your computer, share websites with a bit of preview text, or embed video and audio files from elsewhere on the web.
This means it will appear to anybody who views your profile, and in the community tab if your site has it enabled, as well as in the network tab of any of your contacts.