Simplify the following text for a Grade 12 native English-speaking person.
Original: The World Health Organization 's ICD-10 lists avoidant personality disorder as Anxious ( avoidant ) personality disorder .
Simplified: Avoidant personality disorder ( AvPD ) is a type of personality disorder and mental illness . People diagnosed with Avoidant personality disorder are socially inhibited , meaning that they are shy and afraid of social situations .