The AM3 tracker detects movements of the body when you sleep, for example when you turn over or when you get up during the night. These movements are then converted into "awake periods". Knowing the duration of your awake periods can help you better understand the effectiveness of your sleep.
*credit to Sylvain of iHealth Labs EU
https://helpcenter.ihealthlabs.eu/hc/en-gb/articles/205909731-iHealth-AM3-Awake-periods