I think you would benefit from reading this page:

https://earth.esa.int/handbooks/aatsr/CNTR2-6-1-1-5-2.html

If this is not the answer that you are looking for - could you be more specific in your question?

HTH

I depends of the raster format. As an example, a GeoTIFF is a standard .tif format that includes additional spatial (georeferencing) information embedded in the .tif file as tags. These tags can include the spatial extent, coordinate reference system, spatial resolution, no data values, number of layers (bands)...

Read more about it here:

https://www.google.com.br/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&uact=8&ved=0ahUKEwj82uP6hZbVAhUJFJAKHW9JAZAQFgg2MAI&url=http%3A%2F%2Fmac.mf3x3.com%2FGIS%2FGEOTIFF%2Fgeotiff_spec.pdf&usg=AFQjCNFwyS3OY7Zz0VHJCR29FjwNek76Hg

Best,

Longitude and latitude values are assigned to a ground location via trilateration. We have about 30 GPS satellites rotating around the earth, whenever three of this satellites intersect, based on the differential distances between your GPS receiver and the satellites, the value obtained is your longitude and latitude value. The more satellites are in view to your GPS receiver, the more accurate is your GPS location.  For more details see https://www.maptoaster.com/maptoaster-topo-nz/articles/how-gps-works/how-gps-works.html and http://gisgeography.com/trilateration-triangulation-gps/

For how a pixel in a satellite image is assigned a longitude latitude value, this article will shed more light www.mdpi.com/2072-4292/9/1/90/pdf and http://spot4.cnes.fr/spot4_gb/attitude.htm

Best wishes.