just like a mountain, it is a pictography.
The big seal script of the character is
Similar to shell bone script.
Then it changed a little bit in Small Seal script （2000+ years ago)
is still similar as that of Shell Bone script, but the lines are more straight.
Then the character became to Clerical script (about 2000 years ago)
The Clerical script has changes in width of the line, which could only be done by brush, making the character very beautiful, and unique from all characters written by pen.
The song typeface - standard printing script nowadays is
I have made a video for this character on youtube, you are welcome to watch to learn more, especially you can hear the pronunciation of the character.
Learn Chinese characters from pictography: Lesson One 山