Time series data refers to a series of data points that are recorded and indexed in chronological order. This type of data allows us to analyze patterns and trends over time, providing valuable insights into the past and future performance of a particular entity or phenomenon. By studying time series data, we can make informed decisions in finance, such as predicting market trends and identifying potential risks. It is a fundamental concept in the field of finance and is used extensively in various industries for forecasting and analysis purposes.