「多分」 means 'probably' or 'maybe'. You use it to express uncertainty or likelihood, suggesting that something is likely to happen or be true, but not 100% certain. It's often used at the beginning of a sentence.

確実(かくじつ)ではないけれど、可能(かのう)性(せい)が高(たか)いことを表(あらわ)します。