Hi Marcelo,
Welcome to the wonderful world of the C programming language. This forum is for GCC specific issues, and your questions are more related to learning C than they are GCC in particular -- there are much better forums and websites devoted to C tutorials and getting started.
teste2.c should not have a main function in it, since that function is in teste1.c source file.
Compile your source files: gcc -o myapp teste1.c teste2.c
Run your program: ./myapp
Enjoy, --Eljay
