What kind of cockatiel do I have?

We recently adopted a stray cockatiel, and I'd love to know your opinion on what type of colouring this is, if they are a male or female, and how old they might be. Weight is 106g. I'm struggling to decipher all of the info online! We have an appointment with a specialist vet for a check-up and to hopefully learn more, but I'm impatient :)