23 Strings library [strings]

23.3 String view classes [string.view]

23.3.1 General [string.view.general]

The class template basic_string_view describes an object that can refer to a constant contiguous sequence of char-like ([strings.general]) objects with the first element of the sequence at position zero.
In the rest of [string.view], the type of the char-like objects held in a basic_string_view object is designated by charT.
[Note 1: 
The library provides implicit conversions from const charT* and std​::​basic_string<charT, ...> to std​::​basic_string_view<charT, ...> so that user code can accept just std​::​basic_string_view<charT> as a non-templated parameter wherever a sequence of characters is expected.
User-defined types can define their own implicit conversions to std​::​basic_string_view<charT> in order to interoperate with these functions.
— end note]