Cosplay for all intents, is dress up / costuming as a general term
more in depth would be the making(key word) of a costume for the purpose of display or wearing to show your skill and accuracy during an event. EG comic con, Dragon con or others. more true cosplayers will compete in shows that show the detail of their costume in front of a panel at a convention.. I don't do that.. I enjoy making and displaying at home fro my own amusement or handing out candy at trick r treat