T12 is a standard for a specific type of soldering station/tips. The original tips from Hakko are called T15 but they are interchangeable.

When you read about T12 stations it means they all use specific tips; these tips are popular because they perform very well, are cheap, and can be found all over the place.

The Chinese have copied Hakko's technology, applied it to their own soldering stations and made it readily available for a fraction of the price as compared to the original station from this company.

This is the one I would recommend: Quicko T12-956 which is affordable and performs great.