Yes, tell them about Savers, the currently Japan only series.
Okay, I'll summarise the genrality of all the series:-
Digimon are beings from an alternate world. The Digital World. It's creation and basis of existance changes from series, though 9/10, it's made of data from our Internet, and connected to it somehow.
The series follow the adventures of a group of 6-15 year olds, with adults for the occasional bit of originality(Savers stars an eighteen year old).
These people are called Digidestined, and always have some form of Digivice, as well as, bar the fourth series, a Digimon partner. In the fourth series, the Digidestined become the Digimon.
The Digivices allow for Digivolution, which allows the partner Digimon, or human in Frontier, to advance a level, from Rookie, to Champion, then Ultimate, then Mega and onward in some cases. In Japan, it goes Child, Adult, Perfect, Ultimate, Super Ultimate, and in Frontier, Pico, Human, Beast, Fusion, Union, Susanoomon(Only Digimon that high a level).
The basic plot boiled down is either the Digital or Human Worlds are in danger, and these people by some twist of fate are chosen to save it(hence Digidestined). They defeat various evil Digimon, make alliances with other Digimon, and thene eventually an even bigger twist leads to both the Digital and Human world's being threatened. By this time we know of, or are getting close to, discovering the uber evil Digimon of the series in question. Then, through teamwork, the final badguy is usually defeated by the strongest Digimon of the group, typically involving the main character's Digimon's Mega/Ultimate form.
The series are as follows, with characters and main partner Digimon in brackets:
Digimon: Adventure 01(Tai, Matt, Sora, Izzy, Mimi, Joe, TK, Kari, Agumon, Gabumon, Biyomon, Tentomon, Palmon, Gomamon, Patamon and Gatomon)
Digimon: Adventure 02(All of the above plus Davis, Yolei, Kody, Ken, Veemon, Hawkmon, Armadillomon and Wormon. There's also more Digidestined fro around the world, but they're not too key to the series until near the end)
Digimon: Tamers(Takato, Rika, Henry, Jeri, three other guys, Henry's little sister, two toddlers, Guilmon, Renamon, Terriermon, Leomon, Cyberdramon, Guardramon, MarineAngemon, Lopmon and Impmon)
Digimon: Frontier(Takeru, Kouji, Izumi, heftily built kid, young kid with big hat, Kouchi, Agunimon, Lobomon, Kazemon, Beetlemon, Kumamon and Lowemon)
Digimon: Savers(Maseru, blonde guy from above, girl, ninja kid, Maseru's sister, boss guy, two tech workers, Agumon, Gaomon, Raramon, Falcomon, Biyomon, Kudamon, BlackPawnChessmon, WhitePawnChessmon)