Word Wrap
With Word Wrap turned on your entered text will be wrapped at the column you specified in "Special | Setup Xnews - Compose". This is a good idea since your text will be quoted by others who get quoted themselves and so on. To keep the full story readable a common value for the line wrap is 72.
So why do you can turn this wrapping off? When posting an URL you should keep it on one line and wrap the rest of the message manually. Wrapped URL's often don't work in your browser.

Keep Copy
Sets if your own postings are copied to the Sent folder. Make this permanent by filling the corresponding field in "Special | Setup Xnews - Compose".

Full Screen Edit
Blinds out everything except the ruler so the screen is all yours to type and type and type.

Use External Editor
If you don't want to use the Xnews buildt-in editor e.g. because your are used to a special text-editor or want to use spell-checking from there you can use another one you specified in "Special | Setup Xnews - Compose". From the Edit window choose "Use External Editor" to open that editor with the text you typed so far. After writing, save the text and return to Xnews. Xnews has replaced the text in the buildt-in editor wih the one that comes from your other editor.

Send
This one sends your message to the server

Save
You can save your posting to the outbox to send it later. When you close Xnews with the Outbox containing saved messages, next time you start the program the Outbox will be the first thing you see. This is to remind you to send your messages.

Stop
If you have typed a *lot* of text or are going to post a binary the sending will take more than the usual part of a second. That gives you time to re-think: Did you write nonsense? Are you posting your binary to a non-binary group? If you can answer this with "yes", you may want to use this Stop command and the sending stops immediately.