Digimon adventure started in 1999 and it is the first season in the digimon franchise, It involves a group of boys and girls being taken to a parrallel reality called the Digital world, when they are at summer camp. They were taken because they were chosen to become Digidestined, the children who would save the Digital world and Earth (near the end of the series) from the evil forces that threaten to destroy it. 

Each of the children get a digimon partner who are programmed to be bonded to them as well as miniture devices called digivices. With the power of digivices their digimon partners can digivolve into stronger forms to battle enemies and save their partners from danger.

Although they originally fight in the digital world to get back home, they eventually vow to save the digital world for their digimon friends, as the plot thickens the children deal with things that they are dealing with in the human world and they mature. Each child recieves a crest that defines a particular trait about them and their power helps their digimon partners to digivolve to the next level. 

It is later revealed that they were chosen because they all saw the greymon and parrotmon incident that happened in digimon the movie that these traits were the strongest good trait within their personality. Tai was always courageous, Matt was always a good friend, Izzy was knowledgeable even back than. Joe was highly reliable. Sora was loving and caring, Mimi was sincere about what she thaught weither the thaughts were positive or negative. TK was always hopefull and never willing to give up and kairi was just good and always wanted to do what was right.

Eventually evil digimon became coming to the real world by crossing a dimensional gate from the digital world. The digidestined and their partners followed, they landed in the childrens home town Odaiba Japan. As the digidestens battle the evil on earth they are joined by an eighth member who was kairi kamiya, Tai's little sister. While this was going on four Mega Level Digimon called the Dark Masters took over the Digital World and the Digidestiened have to fight them one by one and eventually they have to fight their real enemy Apocalymon, the digimon who had made all the evil digimon that the digidestined had previously faced.

When Apocalyptmon was defeated the digidestined went back to the real world, leaving their partners but they would reuinite with them in the digimon movie 'Our War Game!'