Cloud Cover


I am quite new to this… So this is a very naif question:
When choosing the options in advance search in mission S2, one can chose a value to the clou cover. What does one choice implies ? Does this mean that we will get images in wchich the cloud cover is between the values we have chosen? And if we are taking BOA data, does it make any difference at all?

A rough estimate of the cloud cover of each S2 product is written in the metadata, but this is no exact value, but rather a help to search for usable data.

BOA data (L2A) is not automatically completely fee of cloud cover, it is just corrected for atmospheric conditions at the time of image acqusition. If there is a thick cloud in the TOA data, it will also cover the BOA data.

Thanks, the more i read, the more i realize how complex this things are.
Would you rather use TOA data and “clean” it using costumized algoritms or just use BOA data.
Is there a big difference between the 2?
Thanks again.

if there is L2A data available, I would use it. But you can produce L2A from L1C with sen2cor. The differences are discussed here SNAP Tutorial