GENERATORS are the source of most items in Love & Pies.
Often you create them yourself by merging certain items together. For example, you can merge together Shopping Lists and Empty Bags until you get a full Grocery Bag generator.

TAP on a generator, and it will create specific items. The grocery bag, for example, creates Bags of Flour and (more rarely) Apples. You can then merge these items together to make different food items.

If you tap on a generator enough, it will temporarily run out of items and need time to fill up again! At this point, you can either wait and come back later, or you can spend some diamonds to refill immediately.

To refill the generator using diamonds, look at the INFO PANEL located right at the bottom of the screen.
If you have a generator selected, you will see a green button that says "Skip". If you have enough diamonds, you can press this button to refill the generator.