Observing data over time is time series. Predicting that data in future is time series modelling. Unlike the regular prediction, this is slightly different because of the chronology in the data.
As an example say a retail outlet (call it RetaileR) observes the daily sale of goods from when the company was created. It has been 5 years since, and they wish to estimate the sale for the next year for two reasons
- to assess the strength of the company and its future prospects
- to optimise its inventory stock and prevent losses due to undershooting or overshooting the estimate