explicit in c 2b 2b meaning

1class String {
2public:
3    explicit String (int n); //allocate n bytes
4    String(const char *p); // initialize sobject with string p
5};
6

1class String {
2public:
3    String(int n); // allocate n bytes to the String object
4    String(const char *p); // initializes object with char *p
5};
6

1String mystring = 'x';
2