Proficiencies are required to use weapons effectively. Without proficiency in a weapon the difficulty of any weapon is doubled. Skill points are spent towards a proficiency. The number of skill points required to gain a weapon proficiency is equal to the Weapon Difficulty/5. At character creation it is not possible to have partial proficiency.
All characters start with a basic proficiency in Brawling skills, which comes at no cost as a Melee Combat proficiency. Likewise, throwing basic and simple objects does not require proficiency.