Typically a financial forecast utilizes a straight line or a historical running average to estimate the financial performance for the remaining months of the fiscal year.
In addition, year over year numbers may be utilized in the forecast. This is typically done for business that are cyclical in nature. For example, you may hear a reference to 'compared to same period last year' or 'quarter over quarter' performance.
A prediction is simply a guess. A prediction can be based upon fact but it can simply be someone's intuition or best guess.