In Google Earth Engine we usually load an image collection first and then filter it by a date range, a region of interest and a image property with some cloud percentage estimates.
If the cloud threshold value is set too low it may happen that we throw away (filter out) to many images that could have been useful for our analysis. If we select the filter too generously, too many scenes with clouds remain. Finding a good threshold is not easy, this blog post may help to find it.
