Near the start of the game, you will be given a central mother base to use for a number of different things. It is here where you can save your game, develop weapons, and embark on quests. At the Mission Selector screen, you can replay previous missions to gain a higher score and also participate in extra ones not necessary to the main story. Developing and upgrading weapons is done by spending currency known as GMP, which you obtain doing quests. At Mother Base, you will be able to assign your MSF staff into different teams depending on their abilities and skills.