1st degree murder: intent and premeditation
2nd degree murder: intent, but no premeditation
manslaughter: no intent, no premeditation, but the killer is still to blame for the death
Culpable homicide is a general term that includes all of the above.
I think a drunk driver who unintentionally kills someone would usually be charged with manslaughter, not 2nd degree murder, but it might depend on the circumstances and the prosecutor.