S1tbx, .cos file

Hello everyone. I need an explanation. What is the utility to have the .cos file in analysing a SAR product with SNAP?
Thank you for the replies.

in case you are talking about TerraSAR-X, the complex information (amplitude [i+q] and phase) of SLC products is often stored in a matrix format of a cosar file. GRD or MGD files which are only representing backscatter intensity can be stored in GeoTiffs more efficiently.

It is rather a question of product level. Please have a look here: GTC (Geocoded terrain corrected) data

Thank you for the answer. I’ll go to the topic you sugget.