Why do I see a lot of .dSYM files in my archive>dSYM folder?

Question

I was analysing a crash and I noticed I have a lot of .dSYM files in my dSYM folder inside archive package,

below is the image of dSYM folder from my archive showing all the contents inside it.

Also

I noticed there is only 1 file with the name of my project that I think I will be using to symbolicate my crash, I wonder what are other files used for and why are the generated?

Note: I created a default iOS project (named "test") using Xcode 8.3.1 to recreate this observation.