STDs or STIs caused by bacteria are usually easier to treat. Viral infections can be controlled, but they can't always be cured. Getting an STI, even an incurable one, can be manageable. Many are treatable, even curable, with antibiotics or antiviral medications, and some STDs go away on their own.
Genital herpes is a common STD, but most people with the infection don't know they have it. While there is no cure, there are medications available that can prevent or shorten outbreaks. These medicines can also make you less likely to transmit the infection. Bacterial STDs can be cured with antibiotics if treatment starts early enough.
Viral STDs can't be cured, but symptoms can be controlled with medicines. There is a vaccine for hepatitis B, but it won't help if you already have the disease.