The aim of this new game is to raise up Magikarp to compete in jumping contests and eventually defeat all of the jumping Leagues. You can train the Magikarp by feeding it berries and partaking in special training regimes. You can find out more information in the trailer below:
The game is free to play but there are in-app purchases for diamonds which can then be spent on items (there is a hard limit of 5,000 diamonds being the total you can buy). The diamonds can also be obtained through playing the game though, so you don't have to buy any.