Dynamics in music refers to how loud or soft (quiet) a sound is.
In the Hall of the Mountain King- Edvard Grieg
In this piece of music the dynamic is piano (an Italian word meaning soft or quiet). It's is so soft that you might not be able to hear what is going on straight away. Throughout the piece the dynamic crescendos (an Italian word meaning gradually getting louder). By the end of the piece the dynamic is very loud.
It's Oh So Quiet- Bjork
In this song Bjork switches between piano (soft) sections and forte (loud) sections.
Have a listen below...