Unix C/C++ programs are very finicky about the compiler and library versions. Compiling is the process of translating human readable code into a binary executable or library that contains machine-friendly instructions. Linking is the process of telling multiple executables or libraries how to talk to each other.
gcc is a GNU C compiler that is typically used on unix systems. g++ is a GNU C++ compiler on unix systems. libstdc++ is the GNU standard C++ library. glibc is the GNU standard C library. When you install GCC on your unix machine, you are installing a package of the aforementioned items. The gcc unix command is smart enough to call either the gcc compiler or g++ compiler depending if you pass it C or C++ code.
If you attempt to run your program with an older standard library than it was originally linked it with, your program will crash and complain. Here are some tips to get around it.