Serosorting involves sex between people who choose sexual partners who share the same HIV status as them. An example of serosorting practice would be an HIV positive person choosing to engage sexually with another HIV positive person, and the same applies to a HIV negative person engaging sexually with a HIV negative partner. Serosorting is thought to reduce the risk of acquiring or transmitting HIV as partners share the same HIV status (negative or positive).
The key to serosorting is actually knowing both your HIV status and your partners’ HIV status. HIV infections can still occurs using serosorting when people think they are both HIV negative but one person isn’t. Serosorting also offers no protection from other STIs.