Ballad

A ballad is a song focused more on being mellow.

Criteria
The criteria is fairly subjective. But this kind of song form can vary by genre. However some genres focus more on ballads, such as country.

Ballads occasionally tell stories, but mainly they are high-end love songs.

Culture
Radio has a high tendency to play tracks in this form. Despite being the opposite of dance music and heavy metal in terms of tempo and tone, people often slow dance to slower songs that are otherwise not dance music.