In a recently published article, the Associated Press lead with the headline Biden meets with Democrats as $3.5T plan faces party split. (Multiple other news sources followed.) However, nowhere in the article does it seem to make clear what a "party split" means. Is it a broadly understood term?

Are they referring to a partisan split, where the existing parties disagree, or are they referring to some division within a party that threatens party unity of one or more parties?.

Assuming the latter, how is the disparity between centrists and left-wing democrats a split any more than maybe typical when a range of conflicting views are present?

Is the real story here the conflict between the Democratic leadership's goals and the majority of the party's goals, e.g. a split with leadership?

Note: the headline has been updated to now read: Biden presses fellow Dems: Resolve party split on $3.5T plan. Seems clearer now to me.