The inner child is a term used to describe the emotional needs of you when you were little that sadly, went unmet by your caretakers and pop up today to remind you that you need to nurture yourself at that age. Meaning that you need to look at what you endured and what you deeply longed for at the ages you were abused. I got this concept early in my recovery reading an ancient book called the inner child by a pioneer in the field, Dr. Charles Whitfield. It was so illuminating that even though i was near the beginning of my recovery everything rang true on a deeply feeling level as well as an intellectual level.
Once you understand what it is that you needed that you did not get during your childhood which is first and foremost, love, joy, and safety. You will explore what you liked as a child and what you can DO to make yourself feel safe by doing some of the things that made you happy at that age.
This is pretty succinct so i hope it helps you.