Is there any kind of handy tool to check c++ syntax language reference inside IDE?

what I mean is a kind of scenario like this:
I`m reading  under picture piece of code. 
i don`t know what virtual mean in c++,
so,i want to just move my cursor on the "virtual" text in the code .so i can brief know what does virtual do in c++.

something like this little handy box in the picture:
it jump up with user define stuff.
but by default the IDE assume user know the C++ language syntax.

this will greatly help beginners` efficiency !