In California, like in most states, there is first degree murder and second degree murder. While they both involve an intentional killing, one is more serious than the other, especially when it comes to sentencing.
To put it in context, California groups all crimes that involve taking a human life under the title of homicide.
Within that category is both manslaughter and murder, which can both be subdivided into several categories. Focusing on murder, the difference between first and second degree rests primarily on one thing: intent.