"The Archer Queen is an eagle-eyed warrior, whose weapon of choice is a modified X-Bow that few men could dream of wielding. She can attack enemy villages or guard your village."
The Archer Queen Altar is basically a Barracks/Army Camp/Laboratory for the Archer Queen. When she isn't engaged in battle, the Archer Queen can be seen pacing around her altar or sleeping on top of it to regenerate.
If you wish to see her targeting range, click on the Archer Queen herself rather than on the Altar.
Defensive Strategy
A good place to put the Archer Queen Altar is by your Town Hall, so if enemies approach the Town Hall, she will auto-target them.
If farming (or just treasure-hording) it is a good idea to put the Altar either in the middle of your storages or right next to them.
Offensive Strategy
Lure her out with single Troops until she is out of range of other defenses, then mass deploy troops to kill her.