The %ToName macro inserts the name from the first entry in the To: header, so if you write a message to: Roelof Otten <rotten@isp> the macro will get you 'Roelof Otten' and the %ToFName macro will return 'Roelof'.
However, when you only use rotten@isp the %ToName will try to deduct a name, but won't get any further than the full address, while the %ToFName macro will take the part before the @ and when that part includes a dot (like r.otten@isp) it'll take the part before that dot (a mere 'r' in my example)

You want TB to use the info from your address book, that can be done, but you've got to tell that. That's why there is the %ABnnnPPP macro, where nnn can be substituted with To, From, OTo, OFrom (depending on the address you want to use) and the PPP part must be substituted with Name, Address, Handle (see the help for all options)
%ABToName returns the name for the To: address that's stored in your address book
%ABToZip returns the Zip code for the To: address
%ABReplyBirthday returns the birthday for the address in the Reply-To: header

I hope this helps. Please use the help file to explore all options for this powerful macro.