Because I think you don't have the knowledge others on this site believe you have, I think my answer Will help you the most, but it's a simplification in order to make you intuitively understand what is happening.
The electrical fields (changes of value of electric field, before people start downvoting) are constantly being "created" by electrons even if they are not moving. Those fields are constantly flying away from the source. But because the 3 spacial dimensions of our universe, they are getting smaller in value by distance squared. This is why the electrical field is stronger, the nearer you are to the electron and gets considerably weaker when you move away from it.
When you start moving the electron, you Will see that change in electrical field only after that change in electrical field Will reach you with the speed of light.
Now, when we have alternating current in the antenna, that is generating a changing magnetic field around that current, that is then flying away from it at the speed of light. As we know, changing magnetic fields generate a changing electric field and that generates a changing magnetic field again....
The energy carried by a changing electric and magnetic field is quantatized by what we call a photon. But things get much more complicated from here on.