While the meeting was a personal one, the idea behind it was professional. People close to the two actors have asked them to join hands to cross promote their films, 3 Idiots and Paa.
They met up for a while and Aamir's blog said that he would definitely be catching Paa. While the cross promotion may not work since 3 Idiots already has a fixed plan, they're still trying.
Amitabh and Aamir haven't always been on good terms in the past. While Aamir has always wanted to work for AB Corp as he respects Amitabh, he passed some candid remarks over Amitabh's Black and the issue was blown out of proportion when Aamir's Taare Zameen Par released. However, the two patched up because Amitabh attended Jaane Tu Ya... Jaane Na's premiere last year.