What is std? i don't understand.

Sexually transmitted: An std is an infection transmitted by sexual contact, including vaginal, oral or anal intercourse. There are many std's, including viruses, bacteria, and even some parasites.

Infections that are: Spread through sexual contact. Examples: chancroid, lymphogranuloma venereum, mycoplasma genitalium, trichomoniasis, crabs/pubic lice, scabies, herpes, human papilloma virus (hpv), hepatis b, hepatitis c, hiv/aids, chlamydia, gonorrhea ; syphilis.