"Amateur" refers to non-professional individuals or actors in a porn video. This usually implies that the participants are not paid adult film stars, but rather ordinary people or newcomers to the industry.
"Blowjob" is a common sex act where one person stimulates another's genitals by using their mouth, usually focusing on oral stimulation of the penis. In the context of porn video tags, this means that the video will feature at least one blowjob scene.
"Twinks" are young, slender, and often effeminate-looking gay men. The term is used as a descriptor for individuals with this appearance or those who find such appearances attractive. In the context of porn video tags, this signifies that the video will feature at least one or more participants fitting this description.
So, the tag "amateur, blowjob, twinks" means the video features non-professional participants engaging in oral sex with young, slender, and often effeminate men.