When a Christian prays, invokes Jesus's name or consults Scripture in response to a "fiery dart" in their thoughts they have engaged in spiritual warfare. Also, coming against spiritual ignorance or satanic oppression in the greater world with prayer is spiritual warfare. An example might be praying for revival in a specific community, or perhaps even in the healing of our nation after the recent heated election. This is spiritual warfare in a broad sense, and likely many Christians have likely engaged in this discipline without identifying it as spiritual warfare per se. Also, many Christians with mainstream Protestant or Roman Catholic backgrounds may not even be familiar with the concept of spiritual warfare.
For an individual, spiritual warfare is a discernment or awareness of a demonically aided thought (bondage or stronghold) in ones mind and then coming against it by the power of the Word (Jesus name) or the Word in Scripture. The three areas of spiritual conflict are: (1) the church, (2) the heavenly realm and (3) the mind.
The heavenly realm is the unseen spirit realm that shadows the real world. It is the spiritual ambiance that surrounds us-- containing the "powers and principalities" which St. Paul warns us of in Ephesians.
The battleground of the Church is the coming against the spirits of fear, ignorance and jealousy that fractures Christ's body into thousands of competitive denominations and dogmas.
And the battleground of the mind has to do with progressively eliminating spirits of worthlessness, hopelessness and helplessness from our thinking. These spirits reside in "strongholds" in ones thoughts. Some call them "bondages" and they are manifested mainly as a demonically abetted "voice" in our thoughts. It is the voice that tells us that we are scum and that there is no hope, etc. It is the voice we have all heard and heeded from time to time,
There are also two very specific types of spiritual warfare; (1) the Roman Catholic Church's rites of exorcism, and (2) "deliverance" - as practiced by some ministries with mostly Pentecostal or Fundamentalist roots, The two disciplines have similarities but exorcisim is the actual expelling of a demon from one possessing an individual, and the other has to do with breaking bondages in people already possessing the Holy Spirit. It should be noted that those who have accepted Christ as their savior, and thus have the Holy Spirit living in them, cannot be inhabited by a demon. However, they are still subject to being tempted and tormented by demons much as Christ was by Satan in Luke 4.
In Matthew 10:8 Jesus commissions the apostles (and us) to engage in spiritual warfare. This is a command that all serious Christians should heed. The gain for us is not just in defeating Satan, but its also in growth toward spiritual maturity--toward Christlikeness.
My book Satan's Top Ten Tricks is totally about spiritual warfare, and its sequel Jesus v. Satan: The Message of the Wilderness Temptations is an extension and expansion of the earlier book. Both are available from Amazon.com..