Ahch-To is an aquatic planet with numerous islands which served as the origin for the Jedi and is the location of the first Jedi Temple. It was also home to Jedi Master Luke Skywalker, who went into self-exile seeking the Ahch-To Jedi Temple after most of his new generation of Jedi Knights were killed by Kylo Ren and the rest of the Knights of Ren.
Rey travels to Ahch-To to find Luke Skywalker and it is on this planet that she receives her Jedi training from him. Although Luke is reluctant to train Rey, he agrees to do so until he dies, sacrificing himself to save the Resistance.
When Rey discovers her family lineage, she goes to Ahch-To to live in exile out of shame of her heritage. However, she is convinced by Luke's Force ghost to not her heritage define her and confront Palpatine, giving her his old X-Wing which she uses to travel to Exogol.
- Ahch-To Jedi Temple: A Jedi Temple is hidden on Ahch-To; it was the first of many temples built throughout the galaxy, it was established and maintained by the Jedi Order; it is one of the few Jedi Temples that were not destroyed by the Galactic Empire in the Jedi Purge, and the Galactic Civil War respectively. Based on what had been seen in Star Wars: The Force Awakens and Star Wars: The Last Jedi respectively, it looks like the Ahch-To Jedi Temple had been abandoned by the Jedi Order; even before the Clone Wars, the Jedi Purge and the Galactic Civil War respectively began.