During every cycle, the uterine lining (endometrium) gets thicker to prepare for a fertilized egg. This is a natural, normal, process for every woman that is of fertile age and not using any hormonal birth control. A period is when the uterus releases the uterine lining, as conception did not take place (e.g. the woman did not become pregnant), and when you may need to use a product such as a tampon or a pad, or another product of your choosing.
The period marks the start of a new cycle and is the 1st Cycle Day (CD1). Cycle Day 1 is shown in the app in the Daily, Month, History and Graph views by the period logo displayed on the days where you have added 'period.'
The length of your period may vary from cycle to cycle – on average, our Cyclers’ periods last 4 days. You can also experience spotting during your cycle, which is not the same as your period. You can read more about spotting here.
In the My Cycle (statistics) tab, you can see detailed information about your Period-data, such as how long your bleeding usually lasts, and how often you get your period (the average length of your cycle). See this article to read more about the My Cycle tab and what you can learn from it.