Answer:
There are at least two different foods referred to as curd. One is milk curds used to make cheese. To make those you should heat milk on the stove to almost boiling and add a curdling agent like vinegar or lemon juice. Let the milk sit and them you'll see the curds form.
Then there are lemon curd and lime curd. These are sweet spreads that are flavored with lemon or lime juice and the zest of the fruit. These are like a pudding cooked with eggs, sugar and the lemon or lime juice and zest.