for some things. in most parts of the world they did not (for example) sell the products of their own farm and then use that money to purchase food. they worked on the farm and then processed the produce and then ate it. the lord took some of it.  they did not (for example) normally sell all the tools and furniture and clothes they made, and use the money to buy the tools and furniture and clothes they needed, they made what they needed and traded for the rest. the lord typically bought these things as needed, which was a source of income for the peasants if they made good things.  their whole lives didn't revolve around money in anything like the way ours do. they did have it, but it wasn't just like us but with smaller numbers.
Ireland