The string type is a direct interface to the same type in C#.
Strings are considered an object rather than a primitive, and as such one should use the corresponding object components and ProtoFlux nodes to interface with them. However, if one needs to choose a difference between a reference and value for the string type, it is a value.
Strings are sequences of chars, and as such are UTF-16 encoded. When representing characters that are outside the Basic Multilingual Plane, a pair of two chars is used, known as a surrogate pair. Due to this, not every character in a string may be mapped directly to one char, and this can cause confusion when using ProtoFlux nodes on strings containing non-BMP characters. Additionally, stray surrogate characters that are not part of a surrogate pair may not behave as intended.
Most string-displaying components have an option for Rich Text Formatting, which allow users to put in HTML-like codes to change the style of the text.