Can someone explain some C++ stuff to me?

[Kaboom 0]

Can someone explain to me this code? Preferably line by line

struct FCharacterManagerCharacterInstanceUpdate
{
    inline void operator () (const pair<DWORD,CInstanceBase *>& cr_Pair)
    {
        cr_Pair.second->Update();
    }
};

TTextTailMap::iterator itor = m_CharacterTextTailMap.find(dwVID);
    if (m_CharacterTextTailMap.end() == itor)
        return;

CQuestManager::instance() - what it is (::instance)? I see that in almost every file and I dont get it

when use ChatPacket() or packet.h file?

Like ::instance(), I see very often ::iterator or itor

TGroundItemInstanceMap::iterator itor = m_GroundItemInstanceMap.begin();
CGraphicThingInstance & rInstance = itor->second->ThingInstance;

CPythonSkill::SSkillData * c_pSkillData; - what is c_pSkillData and rest?

CInstanceBase * pkInstMain = NEW_GetMainActorPtr();

why when I change: const float c_TextTail_Name_Position = -10.0f;  to -30.0f, nothing is changing in game?

function(lua state * L) - What is that mean in Lua?

[V0iĐ 97]

I think You should learn C++ first time.