Psychodynamic approaches are talking therapies that explore how unconscious feelings, early relationships and past experiences affect present thoughts, feelings and relationships.
They grew out of Sigmund Freud's psychoanalysis. Modern psychodynamic therapy is usually weekly, less structured than CBT and can run for months or years. Psychoanalysis itself is more intensive, with several sessions a week.
Psychodynamic therapy is not a treatment for ADHD or autism, and it is not one of the approaches NICE guidance describes for either. Some ADHD and autistic adults find it useful for other things, such as grief or relationships. Others find sessions without a set structure hard and prefer something more concrete.
Some older theories blamed parenting for autism. Those theories were wrong and have been abandoned, but they are part of why some autistic adults are wary of this tradition.