You have to be more specific than that. You're asking about an instruction that you do not even know what language we're talking about.
For instance, InitGraph in Pascal initializes the graphics system.
C/C++ has a similar graphics system initialization via initgraph.
There could be many languages or many libraries with a function called initgraph. It could initialize some graphs so you can create binary trees or DAGs or whatever graphs you want.
It really depends on where you've seen this instruction.