When the Bible says "world" it often means the world system. Spiritual beings
as well as people make up this world system. Often the Bible uses the term the
world to define people only, as in Jesus died for the sins of the whole world. In
the second of these two meanings we are told that the world does not know
God. The world is what Jesus came to save, but the world did not accept
Jesus when He came. Instead of receiving their salvation with thanksgiving, the
world hated Him and plotted to kill Him.
Chief among the spiritual creatures that are part of the world is the fallen angel
of light, Satan. He was cast out of Heaven for grasping at equality with his
maker, God. When he was cast out he was cast to Earth. The Bible refers to
him as the prince of this world. He tried to defeat Christ by killing Him (John
14:30), but God raised Jesus from the dead and defeated Satan once and for
all! (John 16:11) Still, Satan roams about like a lion seeking those that he
might devour. The world is a dangerous and treacherous place, yet Jesus
came into it to save us all. In Him we are free from this world system, and His
power protects us.
The scriptures tell us that we are to be in the world but not of the world. I think
this means that we are not to value what the world values, and that we are not
to be too attached to the world, but instead to have our hope focussed on
Christ and His return.