My daffodils have finished flowering now ... it's spring here ....but I've never grown them before and I have a question.

I know that daffodils grow from a bulb, and the bulbs will double if not lifted after flowering and I was told to leave my daffodils where they are until the leaves start to dry off which they've not done yet.

Considering all that, my question is.....

At the top of the plant where the flower was, I see a large green bulb. Does this bulb contain seeds, and if it does what do I do with it? Do I cut the bulb off now while it's green and dry it out, or do I leave it until it dries on the plant?