What is "Spiritual Warfare"? What is spiritual warfare? And how is it different from malefic ("black") magic?

One Evangelical Christian sums it up with, Prayer should not be spellcasting. God is not your djinni.
1 Pet 5:8, KJV:


  Be sober, be vigilant; because your adversary the devil, as a roaring lion, walketh about, seeking whom he may devour


Eph 6:12, KJV:


  For we wrestle not against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this world, against spiritual wickedness in high places.


1 Thess 5:17, KJV:


  Pray without ceasing.


Throughout the NT believers are encouraged to always remember that we are fighting a battle against the forces of evil. The term "Spiritual Warfare" is generally used by those who acknowledge and undertake to accept this calling, "enduring hardness, as a good soldier of Jesus Christ".

Regarding comparisons to "black magic", I would lovingly wish to draw your attention to Jesus' response to similar accusations He faced in Matt 12:22-32. In light of these words from Jesus such terms should not be bandied about since the implications are so very severe.