Main choices are: commercial, private/boutique, female only and more. It will depend largely on your experience level and personality, level of self-confidence, etc.
To illustrate further, take a guy firstly, who has plenty of training experience, not shy and knows what he is doing and doesn't need the assistance of a gym trainer. Then take a female who is not used to being around exercise equipment, lots of people, and generally is quite unsure of herself. She would naturally do better in a private/boutique or female only gym at least to begin with.
These are obviously generalised statements but I see this all the time and after being in gyms myself for over 20 years I see it every day.
Adelaide Personal Trainers