The top part is the aerial, the shiny bit that completes things between the people on the other end receiving and the "lead-in" (the not so shiny bit that connects the aerial to the sender's transmitting gubbins). The antenna is the entire system or assembly (ie; the aerial and the lead-in). To receive, you only need an aerial, because in sepia years, your wireless (another description that has changed) radio didn't even have a transmitter gubbins thing.
During the inter war years, the government dictated that a commercial aerial and lead-in to be no longer that 100ft combined because it knew that the lead-in part radiated and it didn't want its ships sunk by sneaky coastal and convoy watchers. These days though, meanings and definitions have moved and blurred to the point of irrelevance, 'wireless', for instance doesn't mean what it once did. To give you hope, I stand by to be corrected though.
Hours of fun was once had using farm chicken wire on Salisbury Plain on various signals courses chatting to places over the world. Skills came in handy one Xmas Eve though; using 25 metres of farm fence* and PRC 352, by trial and error we eventually got a signal from N Bosnia to the lovely ladies of BT Portishead Radio, who kindly patched us through to our families for a surprise 5 minute phone call each. Working with 2 Scaleys helped and no phone set up for the troops back then of course. Scaley, or Scaleyback was the nickname given to army signallers who had their backs fried by early portable transmission gear.
* From the urgent tone of your contribution, I'm guessing this sort of detail is really important so for the sake of peace of mind, the old farm fence was wire and not wooden.