The powerful Row Evolution feature shows you a chronologically ordered line chart of your analytics metrics for any row in any report. You can view how metrics for visits that use firefox or visits that came from Google or almost anything else change over time. This can enable you to quickly identify any recurring patterns, for example, higher traffic on weekdays, whilst also getting a feel for the overall trend of the metric over different periods of time.
Additionally, you can compare these trends with the trends behind other rows to gain even more insights (e.g. comparing the use of two different keywords over time). This can aid you in understanding how your metrics might impact each other and help you draw conclusions to analytics questions.