Spiritual discernment is a spiritual gift. It is the ability to distinguish between truth and falsehood, in both the natural realm and also in spiritual situations.
To another the working of miracles; to another prophecy; to another discerning of spirits; to another divers kinds of tongues; to another the interpretation of tongues. (1 Corinthians 12:10)
The gift of discernment helps believers identify genuine spiritual messages and discern truth from error within the church and the wider world. It involves the supernatural ability to identify whether a message, teaching, or action originates from God or from another source, such as a deceptive spirit. A key aspect of discernment is comparing spiritual claims with the teachings of the Bible, God's Word.
Discernment is a gift because everyone doesn't have it just as everyone doesn't have all of the Gifts of the Spirit - except Jesus. Just as trust is earned, respect is both given and earned, discernment is given, and it is learned. Christians are encouraged to ask for discernment from the Lord, so you don't walk in ignorance or darkness. But discernment once received from God must be developed, sharpened, honed.