A question about a recipe: Foolproof Ice Cream

I have a question about step 9 on the recipe "Foolproof Ice Cream" from Tammy. It says:

"Churn for 30 mins. If you have any add-ins, add to the ice cream for the last 30 seconds."
what do you mean by churn i dont have an ice cream machine is there a way to make ice cream with out the machine