Your inventory is where you will find all the gifts that other players have sent to you and also any other objects that you may have acquired from completing quests. Some of the items in your inventory may be placed in your town, and others are simply collected in your inventory until they are required, usually to complete a part of a quest.
As a general rule, items with a plain brown background may be placed in your town. Items with a gray or patterned cannot be placed, and will be removed from your inventory automatically when necessary.
All of the following items can be sent as gifts to another player. If they are in your inventory, then you have probably received it as a gift from one of your friends
Special Items are generally one-off items that are gained from completing a quest. Some may be placed in your town, and others may be required for later quests.