If this falls within the category of "gift of prophesy" then here is how it manifested one time, from my perspective:
Every three weeks, in a job I previously held, I used to drive past a place where a homeless man sat, with a sign, seeking alms. I saw him there on the way to and sometimes from that location for the better part of a year.
One day, on the way in, the Holy Spirit said to me "Give him your lunch." I replied, "My lunch? But I'm already hungry." Silence was the response. This was an internal conversation but it is difficult to explain, if you've never experienced it, how that the Holy Spirit's voice plainly did not originate within me and yet appeared in my mind.
I parked my van to enter the jobsite, making a Gideonesque deal with the Lord, "If he is still there on the way out, I will give him my lunch." This may seem like compliance but, actually, I was trying to squirm out of His command since I would be inside for at least three hours and the homeless man was not always there on the way out. I still had silence as a reply.
After finishing my work and getting back in the van I took my lunch (in a classic little brown paper bag), put in the only $5 in my wallet and a small gospel of John pamphlet, and briefly prayed over it ending with a reminder (to the Lord) that the deal (that I had made) only held if the man was still there.
Approaching the intersection where the man begged I could see that he was still there. I began to wonder if I should just toss the bag out to him if the light remained green or call him over if I stopped several car lengths away. I also began to wonder if the Lord would give me a pass in the name of traffic safety (I was very hungry). Needless to say the light turned red and I had to stop right alongside the homeless man's position.
I rolled the window down and called to him, beckoning him over. As he approached I handed the lunch bag out the window saying, "This is for you". He took the bag and reached out to shake my hand saying, "God bless you". As I opened my mouth to say "You're welcome" or some such I was instead very surprised to hear myself say, with startling vehemence, "No! God bless you! He loves you and He has a plan for your life!"
Wide eyed, the man jerked his hand back as though stung, and I am sure my eyes were wide also as I had felt something pass between us in the touch and the words I spoke seemed to come through me rather than from me. The light turned green just then (I could tell by the car horns sounding behind me) and I drove away, shocked. I never saw that homeless man there again.
- As a funny side note, the Conservative Baptist Church I grew up in after being saved was palpably uncomfortable with this and similar experiences!