Pop punk is a genre that, like the title suggests, mixes pop and punk into one sound. Typically combining a fast tempo, often with a punk theme, along with pop-influenced melodies.
Some of the first big name pop punk bands include Green Day, Blink-182, and Sum 41.
Newer pop punk (2015 onwards) also include some emo into the mix, particularly in the lyrics. Bands like this include Neck Deep, Modern Baseball, and The Wonder Years.
Older pop punk tends to be more political, taking more influence from punk than pop, while newer pop punk tends to be a bit more on the poppy side, singing about relationships, broken hearts, and hanging out with your buddies.
Pop punk tattoos tend to be mainly in American and neo traditional styles, along with blackwork.