If you are referring to the New York Penal Code, this is that statute related to second-degree murder. A felony is the more serious level of crime, (the other category is misdemeanor) and felonies are evaluated from E to A, with A being the most serious felony.
I assume you're asking from NY, in which case a 125. 25 is murder in the second degree. This can be a negligent death, depraved indifference or a murder committed during the commission of a felony. It is a class A-I felony, the highest level in the New York penal Code.
This is murder in the second degree in New York. This means that the murder was not premeditated and not committed while committing another crime. The murder was an intentional killing, action with depraved indifference that resulted in death, or while committing a crime causes a death or another participant causes death.