Is there a difference between property and possessions? What is that difference?

Yes! There is a difference. The key determination is between private property, and personal property. I know it sounds semantic, but there are meaningful differences.

Personal property is a belonging of yours that you personally use, such as clothing, a watch, a vehicle, a computer, or a home that you personally live in. Its ownership is defined by use.

Private property is instead something you own because an institution says you do, such as a factory or land that you rent. The only reason you posses it is because you have a piece of paper saying you do, but the use of it is mostly/entirely by others.

Private property is only used to exploit the labour of others to accumulate additional capital, while personal property are simple possessions that aren't used to exploit labour.

If you'd like to get a more thorough understanding of the distinction between the two, I recommend Engels' summary of Marx's Capital it's much more easily comprehensible than the original text, and gets the core points across.

Most anarchists and Marxists believe in the abolition of private property, but personal property is typically kosher (though not with everyone). The idea is that you shouldn't be able to own something that you don't actually use, so something like a factory would be owned by everyone who works there, rather than some capitalist who simply collects profits from afar.