Solo Journaling Games, sometimes also called Solo Journaling RPGs or just Solo RPGs, are a subgenre of TTRPG explicitly designed for solo play. Most are played though the navigation or generation of Journaling Prompts, which are then turned into the written entries that compose the gameplay itself.
While these games are most commonly played though written journal entires, the genre also includes some more experimental and unconventional approaches to gameplay such as sketching, mapmaking, and audio / video recordings.
In Real Things for Real People, Jay Springett describes Solo Journaling games as Jungian psycho-technology, the concept that originally caught my attention and sparked my fascination with Solo RPGs.