That´s right, a lot of planes ar parked in a remote area at FRA. Here´s the reason:
A lot of planes from far away (South Africa, Australia, Namibia) come early in the morning to FRA and fly back late in the evening. They place their planes the whole day at FRA.
But there is no place for them at the gates. FRA has not the capacity to leave the planes the whole day at the docking bridges.
So the airport gives discounts to all Airlines, which allow to put their planes to a remoted parking position. The most airlines use this offer and so, after people left an arrived plane and all necessary work is done, the planes where pulled to the back of the airport, to make place for the next plane, which is sometimes waiting (!) on the taxiway for that gate.
Here are some examples of airlines:
South African Airways
Thai Airways International
... there are much more. But I can´t list all of them.
How you can see, most of them come from Africa, and south-east of Asia. But german Airlines with long stay, use the area too.
One thing: You will never see a plane of Lufthansa Cargo in the remote area.
What you have noticed here is the cargo port of FRA, which is between the mentioned area and the LH hangars.