what does my dream means nightmare

i had a nightmare last night. somethine was happening that i cant recall now, but this is the thing, suddenley i was in my car, and i was in ahurry to lock myself up in it coz i saw someone was trying to kill me or hurt me, and in a blink all i can see is that he either opnes the door, or he break the window with a sort of baseball bat he bangs my head and i start blead, like if in normal life im definitley dead. now the hting is im aware that i should be dead dfor some reaosn s1 i know i guess comes in to the dream and i resist the death thing, and im not panicking, and somehow the blood starts disappearing. it felt so damn real, wht is this?