TEXTURE
In music, texture refers to how the melody, rhythm and harmony combine in an overall composition of a piece of music.
Thick & Thin
Throughout the duration of a song, the texture changes multiple times from thick and thin. The reason of this could be that there are more instruments being used at one time and the volume that they are being played at is increased. The reason for thin texture could be that there are less instruments being played, or more instruments in the background as opposed to the foreground, removing the thick element of texture. Changing texture is a very popular pop music characteristic.