void ISystem::ShellExecute(const char command, const char file)

This gives insight on ShellExecute usage. For example, ShellExecute can launch a website or a word document in the client's default viewer.

vgui\ISystem.h must be included in the appropriate file.

void ISystem::ShellExecute(const char *command, const char *file);
vgui::system()->ShellExecute(...);

command can have one of the following values:

Look here for more information on each of the commands.

file points to the local file or webpage you want to access.

ShellExecute