The player controls Ori, a white guardian spirit. Long ago, Ori fell into the forest and was adopted by a bear-like creature who raises Ori as its child. A malevolent entity, Kuro, appears and takes Ori's mother from him, forcing Ori to explore the forest on his own. Initially, Ori is very weak and can only jump about. During the game, Ori meets Sein /saɪn/, who will both guide Ori on his adventure and attack enemies. As the player gains experience, they may choose new abilities for Ori and Sein, allowing Ori to explore more of the game world.
In addition to save points scattered in the game, players can create "soul links" at any time they choose to serve as checkpoints. However, soul links can only be created using special resources collected during gameplay; the needed resources are not in abundant supply, forcing players to create them only when necessary.
Source: Wikipedia, "Ori and the Blind Forest", available under the CC-BY-SA License.