If you're coming from C, then you need to understand the STL's concepts of "Concepts", "Modeling", "Refinement", and Iterators etc: http://www.sgi.com/tech/stl/index.html (that link doesn't cover C++11, nor even the STL additions in C++03 and TR1; but it is still essential background reading).

When some people say "Modern C++" they mean template meta-programming (traits, partial template specialisation, etc) as exemplified by Alexandrescu's book "Modern C++ design": http://www.amazon.com/Modern-Design-Generic-Programming-Patt... (note that I am not necessarily advocating such techniques, but understanding them will certainly help when you run across them in the wild).

Modern C++ Design (Andrei Alexandrescu)[1] is wonderful, but C++11 has "simplified" much of what he covers. If you want to be able to read the C++11 standard[2] with little effort, Alexandrescu's book is nevertheless a good primer.

[1] http://www.amazon.com/Modern-Design-Generic-Programming-Patt...

[2] http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n333...