It's kind of hard to explain, but from my understanding AvPD involves severe avoidance of social situations in an effort to avoid rejection/embarrassment/etc., feeling like you are more socially inept than you are, etc.
An excerpt from a
website that explains symptoms/behaviours a lot better:
Avoidance of activities at work that involve interpersonal contact due to fear of criticism or rejection
Unwillingness to interact with others unless certain they will receive a positive response
Hesitancy in intimate relationships due to fear of shame
Preoccupation with criticism in social situations
Feeling inadequate and being inhibited in new social situations
Perception of self as inept, unappealing, and inferior
Reluctance to take risks or engage in activities that might result in embarrassment
Autism involves developmental delays, especially social delays, that start in infancy/early childhood, and also involves sensory problems, repetitive and restricted behaviours (like being resistant to change, having strict/excessive routines, etc.), among other things.
You can have autism
and AvPD, there's not really any conflicts between them, and in fact autistic people are more likely to develop AvPD due to the constant negative social experiences we have. I match all of the criteria for it due to abuse and negative social experiences I've had throughout my life, both related to autism and not related to it.