STIs are infections that are transmitted through close body contact, usually sexual. Sexual contact includes fucking, sucking, as well as touching, fingering or kissing/licking a cock, arse or vagina.
STIs can be caused by viruses (e.g. HIV, herpes, genital warts), bacteria (e.g. chlamydia, gonorrhoea), or parasites (e.g. crabs).
Many STI's are easily transmitted even when a condom is used and you will not always have symptoms, so it is very important to test regularly.
The recommendation for Gay and Bi guys is to have a full STI test at least once a year - every 3 months if you have multiple sex partners or casual partners.
The clinic is operated by Auckland Sexual Health and is completely free of charge. To attend the clinic, you just need to be a Gay/Bi Male, i.e. a man who has sex with men.