From left to right...
Lightning Lad, Saturn Girl, Cosmic Boy, Chameleon Boy, Shadow Lass.
At this point in Legion continuity, which appears to be pre-Crisis, they are...
Lightning Lad is believed by everyone at this time to be Garth Ranzz from the planet Winath, but he's actually a shapeshifter named Proty. (In his natural form, he looks like a Founder.) He has electrical powers.
Saturn Girl (Imra Ardeen) is from Saturn's moon Titan, and she's a telepath. Garth and Imra are married at this point in time, and they will have three children.
Cosmic Boy (Rokk Krinn) is from Braal, where he was a champion magnaball player. He has magnetic powers. (I've mused in the past on who would win in a fight -- Magneto or Rokk. I think Rokk is more powerful, but Magneto would play dirty.) He later loses his powers, then becomes the Time Trapper, one of the Legion's greatest villains, in a timey-wimey kind of way.
Chameleon Boy is a Durlan named Reep Daggle. He's a shapeshifter.
Shadow Lass is Tasmia Mallor from the planet Talok. She can project darkness and extinguish light. In my favorite period of Legion history, she's married to Mon-El (Lar Gand from the planet Daxam), who has all of Superman's powers, but instead of a kryptonite vulnerability he's vulnerable to lead.