The Global Address List (GAL) essentially acts as a directory service within SmarterMail that contains a dynamic list of all contact information for every user on a domain. Like a user's regular contact list, the GAL can be synced to mobile devices, like Androids and iPhones, using Exchange ActiveSync. However, the GAL will only sync on a search.
This means that while you wouldn't see an entry from the GAL while browsing your contacts, an entry would appear when you do a search in your contacts list. (Depending on the device used, an option may also be available to save the entry in your contact list.) The reasoning behind this functionality has to do with GAL acting as a directory for the company. For large companies with a very large amount of users on the domain, downloading all entries to a mobile device could quickly get out of hand.