Keeping written, typed, or audio/visual record of one's thoughts, behaviors, dreams, etc. Journals can help confidentially process thoughts and express emotion. Journaling can also help us uncover patterns of thought/behavior that may or may not be life-giving, or help guide problem-solving.
There are many ways to journal. Some write in full sentences with great detail, while others write only short phrases without or without grammar or punctuation. Some keep a journal with specific functions: a Dream Journal, a Gratitude Journal, a Health Journal, etc. Journals may be handwritten in some kind of a notebook or typed on a computer.
Writing is only one method. Journaling can also be done by speaking into some kind of recording device. One could create a Photo or Drawing/Painting Journal with pictures that capture noted moments of one's life, or one's thoughts.