Time series analysis and its applications have become gradually important in various fields of research, such as agriculture, business, economics, engineering, medicine, social sciences, politics and others. Time series analysis comprises methods for analyzing time series data to extract meaningful statistics and other characteristics of the data. The basic concepts of time series analysis will be explained in this book chapter. Time series models are used to forecast the values of a variable based on previous or lagged data. Uneven distances are difficult to handle, so observations are usually taken at equidistant time points. The main challenges in time series analysis are identifying the forces or components at work, whose net effect is manifested in the movement of a time series, and isolating, studying, analyzing and measuring them independently, i.e., while holding other variables constant.