While wigs cover the entire scalp, extensions are made to look and feel like real hair, and simply clip in at the root. This is why Chelsea's hair appears to be various lengths and colors episode-to-episode of Teen Mom 2.
Some doubtful fans insist that Chel-Chel was wearing a wig during the first few episodes of Teen Mom 2's second season, but her Facebook fan page (which Chels is supposedly an administrator of) says "its editing thats why adam is bald some scenes an then head full of hair in others."
Even if Chelsea does wear the occasional wig (which we doubt she'd admit to!), she's in great company. Some of our favorite stars and starlets rock hair pieces, like Nicki Minaj, Tyra Banks, and — of course — Britney Spears!