for your understanding at a higher, non-programmer level -

Code:

cc myfile.c -o myfile -lm
# or maybe gcc
gcc myfile.c -o myfile -lm

The above statement does this
1. preprocesses - meaning it invokes a program to honor the #include directives, #define directives in myfile.c. The name of the program that does this is usually cpp.

2. compile - transform the preprocessed code into assembly language - see pludi's
nice description above

3. link edit - this is done by the ld program. The -lm brings in a library (precompiled shared library of code) called libm. The ld program looks for all of the external symbols in your code (like printf() ) and find the external symbol in a library. Each external function you call has to be tracked down then evaluated by ld. It also finds external variables for you. It packs all of this into a specially formatted file - in "a.out" format or ELF format - or whatever file format your machine uses. There are others.

The final product is compiled or binary code, which can be run directly by the operating system.

The stement aboves means "compile myfile.c, write it out to a binary file called myfile and link against libm". BTW, ld by default, also links against the standard C library, libc, so you do not have to "ask" for it.