The C++17 standard, commonly referred to as C++17, was released in 2017. It brought several new features and improvements over the previous standards, streamlining the language and enhancing its capabilities for modern software development.

In C++, the single equals (=) is an assignment operator, meaning it assigns a value to a variable. The double equals (==) is a comparison operator, which checks for equality. A common mistake is to use a single equals sign instead of a double equals sign when trying to compare values, leading to unexpected behavior.

In C++, the keyword to define a function isn't necessarily a specific reserved word like "class" or "struct". Instead, functions begin with their return type, such as "void" for functions that don't return any value. But it's worth noting that "void" is just one possible return type, and not strictly a keyword exclusively for function definition.

Recursion in programming refers to a technique where a function calls itself to solve a problem. The main idea is to break the problem down into smaller instances of the same problem. This approach allows for solutions to be built incrementally, mirroring mathematical recursion.

The STL set container maintains its elements in sorted order by keys. It automatically reorders itself after insertions and deletions, making it the most efficient choice for maintaining a sorted collection without requiring manual reordering.

Lambda functions, like regular functions, can return values. If the lambda's body contains more than one statement, a return statement can be used to specify which value is returned. If the lambda's body consists of a single return statement, the return type is automatically inferred by the compiler.

Smart pointers, such as unique_ptr, shared_ptr, and weak_ptr, were introduced in C++ to provide automated memory management. They automatically handle the destruction of objects they point to, thereby preventing common issues like memory leaks and dangling pointers.

Single inheritance ensures that a class inherits from only one other class, thus avoiding the diamond problem. The diamond problem arises in languages that support multiple inheritance and can result in ambiguity in the inheritance hierarchy. Single inheritance ensures a clear, linear progression without any ambiguities.

The keyword "friend" in C++ is used to specify that a particular external function or another class can access the private and protected members of the class in which it is declared. This is fundamental to the concept of friend functions and friend classes.

The unique algorithm in C++ STL is used to eliminate consecutive duplicate elements from a range. The range after the unique elements is left with unspecified values.

The swap function in C++ STL allows for a quick swap of elements between two containers. This operation is usually done in constant time as only the internal pointers are exchanged.

Multiple inheritance in C++ allows a derived class to inherit attributes and methods from more than one base class. This contrasts with single inheritance where a class can inherit only from one superclass. C++ supports multiple inheritance, unlike some other OO languages.