Что означает символ t в данном вариативном шаблоне?

#include <iostream>
 
template <typename T>
struct NameOf {};
 
#define DEF_TYPENAME(type) template <> \
struct NameOf<type> {\
    static const char value[];\
};\
const char NameOf<type>::value[] = #type;
 
DEF_TYPENAME(int)
DEF_TYPENAME(double)
DEF_TYPENAME(long double)
DEF_TYPENAME(float)
DEF_TYPENAME(char)
DEF_TYPENAME(long)
DEF_TYPENAME(unsigned)
DEF_TYPENAME(unsigned long)
 
template <typename T, typename ...types>
void printTypes(T)
{
    std::cout << NameOf<T>::value << std::endl;
}
 
template <typename T, typename ...types>
void printTypes(T, types... t)
{
    std::cout << NameOf<T>::value << ", ";
    printTypes(t...);
}
 
int main(int argc, char *argv[])
{
    printTypes(1,2U,3L, 4.0, 5.0L, 6UL, 'a', 8.0F);
}

template <typename T, typename ...types>
void printTypes(T, types... t)
{
    std::cout << NameOf<T>::value << ", ";
    printTypes(t...);
}

template <typename T, typename ...types>
void printTypes(T, types... t)
{
    std::cout << NameOf<T>::value << ", ";
    printTypes(t...);
}

printTypes(10, true, '2');

void printTypes(int a1, bool a2, char a3)
{
    std::cout << NameOf<int>::value << ", ";
    printTypes(a2);
    printTypes(a3);
}

DEF_TYPENAME(float)

void printTypes(int a1, bool a2, char a3)
{
    std::cout << NameOf<int>::value << ", ";
    printTypes(a2, a3);
}

DEF_TYPENAME(float)