Question about 1031 investment property

[Cameron Robert Mozzochi]

I’m just trying to learn about real estate investing and would like to make some money doing it eventually. I keep hearing about people saying you can do a 1031 on a investment property if you live there for 2 years and sell it and keep all capital gains. My question is do you have to pay off the mortgage on that property when you do that. Or would it even make sense not to pay it off first before selling? And what do they qualify as a investment property, how do they know it’s a investment? Sorry if that’s a dumb question I just don’t understand that.