Recurrence is a ubiquitous and fundamental feature in many real world processes. It is present at many scales in time and space, such as in celestial mechanics, alternating sediment layers, thermoacoustic oscillation, cardiac variability, and numerous other contexts. The study of recurrence properties (such as frequency analysis) can provide deeper insights into the underlying dynamical processes in general. A rather novel approach for the study of recurrences is the recurrence plot and its quantification, rooted in the theory of dynamical systems. In this lecture, the basic concepts and the major extensions applicable to various research questions will be introduced and demonstrated. Examples to be discussed will include the temporal change of recurrence properties for identification of regime shifts, for classification, and bivariate extensions for synchronization/coupling analysis.