I don’t understand the concept of being “all or primarily in cash”

I here this talked about a lot and am confused by it. Assuming one has been in the stock market for plenty of years, if you DO recognize a bear market is happening, are you REALLY taking out half or a good majority of your profits in say January/February with all those capital gains? What happened to just holding your stocks especially ones like AAPL or GOOGL that you may have a large amount of profits on already?

Just confused when I hear someone say on TV or etc they are “80% cash” in terms of capital gains