What does processing in a boiling water bath mean?

melissajane10, Nov 17, 11:31am
this recipe sounds good but i don't know what their talking about! it's the last instruction
http://www.food.com/recipe/caramel-spice-pear-butter-256372

davidt4, Nov 17, 11:34am
Put the jars into a big pan of water and boil 15 minutes.A preserving pan would be ideal.It's to sterilise the mixture.

melissajane10, Aug 12, 5:05pm
so you do it to a sealed jar as soon as you put the jam into it?