Hedjwitch the idea of having a shadow was coined by Carl Jung.
It contains parts of us that have been locked away - often as a protection.
Our shadows may contain memories or consequences of abuse,sorrow, self deprecation, shame or aspects of our personality that we subconsciously consider undesirable.
Your shadow often resides in our darkest deepest functioning, in the limbic system and are very connected to our inner child.
Although our shadows are mostly hidden, or pushed back, but unfortunately will often often manifest in our thoughts, emotions and behaviour and have a negative impact, leading to shame, anger, anxiety and many more "negative" behaviours. Although our shadow may contain all the horrors and furies there is precious treasure to be found- in my case creativity and playfulness.
So when we do shadow work we get in touch with that inner part of ourselves and heal.
There are many methods in shadow work, but we need to travel lightly- too much too soon can release a storm of emotions. I suffered childhood trauma, so I regularly spend time with my inner child, so I have the opportunity to bring the love, acceptance and comfort to my past self. This in turn heals me in the present- true time travel.
Move gently through this work, it takes time- many psychotherapists use shadow work, but it has a spiritual dimension too.
So a therapist may use the "empty chair" technique allowing you to have a conversation with a part of your past self.
Shadow work can be done through hypnotherapy, psychotherapy, guided meditation, scrying, journalling,tarot art, dream analysis, and no doubt many more. I am not an expert by an means, and others on this thread may have different ways of working
Most of my shadow work revolves around comforting my inner child, remembering scenarios when I was upset, felt sadness and shame.
I meditate on my inner child, just sit with her, give her a hug, try to empower and soothe her feelings.
After sessions like that my anxiety will reduce, as my inner child was given that understanding and empathy.
I can't post youtube links for some reason but there is a truly magical and healing inner child shadow work video on youtube- lots of others too, but this one is particularly powerful, but gentle and relaxing too.
I think a good place to start if you are new to shadow work.
Inner Child Meditation for Codependency, Lack of Self Love and Negative Programming by Michelle Chalfant