The bible bans several things on the Sabbath.  One is travel, since it says that one must "stay in his placed".  Another is engaging in MELAKAH.  While this is traditionally translated into English as "work", there are a lot of things that constitute "work" in English that are not "MELAKAH" in Hebrew, and vice versa.  If I could sum it up in a few words, I'd describe MELAKAH as creating, changing or destroying any asset of wealthy value.  Nearly all of the 39 acts of labor that define "melakah" do that in some way.  Most of the "rules" that have been developed over the years are simply attempts to more deeply explore what that means.