Cosplay (short for "costume play"), is a subculture centered on dressing as characters from manga, anime, tokusatsu, and video games, and, less commonly, Japanese live action television shows, fantasy movies, Japanese pop music bands, Visual Kei, fantasy music stories (such as stories by the band Sound Horizon), novels, and anything in the real world being unique and dramatic (or their moe anthropomorphic form). However, in some circles, "cosplay" has been expanded to mean simply wearing a costume (Taken from Wikipedia). So basically they are dressing and doing everything resembles to the characters they are cosplaying.

Now Lets compare :

Look at his hair. I wonder how long did he spend to make the hair. Not mentioning the "Duel Disk" in his hand too.

Wow. She is as cute as the anime.

By the way, Misa Amane is character from Death Note manga, anime, and live action series.

Well, Thats it. Hope you enjoy.