pt in paragraph form, usually about 2-3 pages long. Keep the paragraphs short and relatively light.
A treatment usually is included in a "pitch". A pitch usually includes: Title, Date, Name and Contact info of Author, WGA registration number, and number of pages. After the vital info, a premise (2-3 sentence summary of the script) and then the treatment attached as a seperate document.
You might also want to check out Scr(i)pt magazine, they have a great deal more detailed information on treatments and pitches.