STIs/STDs are illnesses passed through sex. There are many types of STIS/STDs, but the common ones are chancroid, Chlamydia, genital herpes, gonorrhea, syphilis, genital warts and trichomoniasis. To avoid STIs/STDs, abstain, be faithful to one partner you have tested with and ALWAYS use condoms when you have sex.
Attribution: Straight Talk Foundation