What is a stronghold?

Have you ever read 2 Corinthians 10 and been puzzled by this passage?

"For though we walk in the flesh, we do not war after the flesh: (For the weapons of our warfare are not carnal, but mighty through God to the pulling down of strong holds;) Casting down imaginations, and every high thing that exalteth itself against the knowledge of God, and bringing into captivity every thought to the obedience of Christ;" verses 3-5

I would think, "What is a stronghold? Do I have strongholds? How do I recognize them in myself and others?" I mean, it's obviously not a good thing. 

So I looked up "strongholds" in the Bible Hub online Strongs Concordance. And this is what I found:

Here is a link to the page:

https://biblehub.com/greek/3794.htm

So... it's used figuratively in this verse to indicate a false argument in which a person seeks shelter to escape reality. 

Wow. Thats a big word that says much. I'm going to just ponder that for awhile.