doubts about calls to builders swap method

In my main I have the following instructions:

message("std::swap");
std::swap(*a, *b);

The strc class has the following attribute:

    Char * data;

Then I put the constructors that use swap below.

strc::strc(strc && o) {
    data = std::move(o.data);
    o.data = nullptr;
    msg("move ctor");
}

strc::~strc() {
     msg("dtor");
     delete[] data;
}

strc & strc::operator = (strc o) {
     std::cout<<o.data;
     swap(o);
     msg("copy and swap =");
     return *this;
 }

 const char * strc::value() const {
     return data;
 }

 strc::operator const char * () const {
    return value();
 }

 void strc::swap(strc & o) {
    std::swap(this->data, o.data);
 }

This is the output to see calls made to builders when you called swap.

 std::swap
 strc: move ctor (one)
 strc: move ctor (two)
 strc: copy and swap = (two)
 strc: dtor
 strc: move ctor (one)
 strc: copy and swap = (one)
 strc: dtor
 strc: dtor

Someone could explain to me the internal procedure that they follow. In move ctor, I understand that it returns an instance where its "data" is the string of a and b in the respective calls, but when the constructor = calls swap (strc & o) I do not know where it is saving data, if in principle I had already saved it in the instance in the move constructor. I'm lost. If someone can explain to me the whole process of std :: swap (* a, * b) and what he does with each call to the constructors.

I put it in debug mode, I see that it moves

   #endif
    {
       // concept requirements
        __glibcxx_function_requires(_SGIAssignableConcept<_Tp>)

        _Tp __tmp = _GLIBCXX_MOVE(__a);
        __a = _GLIBCXX_MOVE(__b);
        __b = _GLIBCXX_MOVE(__tmp);
     }

  template<typename _Tp>
      constexpr typename std::remove_reference<_Tp>::type&&
      move(_Tp&& __t) noexcept
        { return static_cast<typename std::remove_reference<_Tp>::type&&>(__t); }

But I get lost trying to follow it because it creates _t pointers and directions that I can not understand.

Greetings