Linker -how it works

[Ty Tower]

Ok -previous post established  "-l" switch is replaced with"lib"

I had a look at my libraries and most end with ".a" , however the linker outpu I am trying to analyse says in part this:-   "-lpthread -lm"

now I have no library called " libm" whatever and "libpthread" does not end with ".a" ,rather it ends with "so.0"  . Its full title is libpthread.so.0.  

Will the linker still find and use it with that name?

Is there somewhere on digitalMars site which explains this linking process - not that gives me a load of B/S of how good it is ?, but which explains how these switches work like "dmd man" for instance