Yikes! I have to update that page (especially the pictures).
Here's a quick description:
1st pos = Feet together.
2nd pos = Feet apart, side-by-side
(as if to have taken a side step)
4th pos = Feet apart, one in front of the other
(as if to have taken a fwd or back walk)
The above three positons are the most obvious and common in ballroom dancing. Third and fifth position are more applicable to ballet than to ballroom, but ballroom dancers do occasionally refer to them (in somewhat of a contrived fashion).
3rd pos = Feet together, heel of one to instep of other.
5th pos = Feet together, heel of one to toe of other.
To be honest, I'm not a big fan of using the 5 foot positions when describing ballroom movements. It's kind of like discussing the anatomy of a car engine using only the Latin language. You can probably do it, but why would you? It's unnecessarily difficult, and there are other languages better suited for the job.
The 5 foot positions are ideal for the description of ballet because they were created for exactly that purpose. Ballroom dancing has evolved a language of its own, and it works much better for describing ballroom movements and positions. So while perhaps it's not a bad idea to know the ballet positions so that you are prepared when someone speaks that language, in general I would suggest using ballroom language to describe ballroom dancing.
Incidentally, the only reason I used ballet foot positions in my message below is because I was quoting someone else. It just so happens that this person used both the ballet foot positions AND ballroom language to describe the steps, so you should be able to figure it out no matter which language you speak.
Regards,
Jonathan