WTF is Loneliness ?

I was watching a podcast , there was this psychiatrist talking about loneliness . He said something very interesting that is "we try to cure our loneliness or other form of discontent externally by getting into a relationship, getting friends , making more money or achieving success. But it is a different internal problem." In this subreddit , So many people post about their loneliness and want to have good friends. We have this assumption that not having friends, girlfriend or boyfriend or any social life is something that makes us feel lonely. I have a question for those who have these things , Do you still feel lonely ?. And if the answer is NO then Do you think that you don't feel lonely because of your social life or Is there any other factor. Let's have some conversation and I want to know your experiences regarding loneliness and your coping mechanisms , May be I am writing this post for coping with my loneliness.