What's new in C++17?

The complete list of C++17 features can be found at http://en.cppreference.com/w/cpp/compiler_support#C.2B.2B17_features.

To give a high-level idea, the following are some of the new C++17 features:

• New auto rules for direct-list-initialization
• static_assert with no messages
• Nested namespace definition
• Inline variables
• Attributes for namespaces and enumerators
• C++ exceptions specifications are part of the type system
• Improved lambda capabilities that give performance benefits on servers
• NUMA architecture
• Using attribute namespaces
• Dynamic memory allocation for over-aligned data
• Template argument deduction for class templates
• Non-type template parameters with auto type
• Guaranteed copy elision
• New specifications for inheriting constructors
• Direct-list-initialization of enumerations
• Stricter expression evaluation order
• shared_mutex 
• String conversions

Otherwise, there are many new interesting features that were added to the core C++ language: STL, lambadas, and so on. The new features give a facelift to C++, and starting from C++17, as a C++ developer, you will feel that you are working in a modern programming language, such as Java or C#.