It means that it is a coil of wire, with 5 turns of the specified gauge, wound on a core, with the core then removed so there is nothing but air as the core. There are instructions on the page for winding the coils.
do you have a diagram for a FM stereo transmitter about 0.5watt
Your government will give you a licence if you use a certified transmitter circuit and will assign a frequency if one is available. It will cost a fortune.
If you make your own transmitter and cause interference with radio stations, TV stations, police, ambulance or airplane communications then you will be in big trouble.