Frames are collectible items with which you will be able to decorate your profile picture or avatar. You can get them by completing Themed Missions, answering topic questions in Temple Trial.
Every time you land on a box containing a question mark (?), you will be able to answer a question on a specific topic. Each topic will suppose a different Themed Mission; the objective is to complete the mission's progress bar in order to get the corresponding Frame.
In the “Inventory” section, you will find your Frames collection and will also be able to equip the one you want, as long as you have already completed the corresponding Themed Mission to obtain it.
In the “Missions” section, under “Themed”, you will find your missions' progress and what you need to complete them.