When you have successfully answered an item multiple times in a row successfully in your reviews it will turn from a new item into a familiar item. A familiar item is an item that you are familiar enough with to be able to recognize it if you see it, provided you have saw it recently.
More precisely, an item becomes familiar the first time it reaches the third SRS stage.
In practice, this means you must answer an item two days in a row within your reviews for it to reach that stage and become familiar.
Some items have other items they are dependent on. These are referred to as dependent items.
For example, a character has the sounds and component items contained within it as its dependent items.
These items will only show up in your lessons once all of their dependent items have become familiar.
When an item reaches the final SRS stage, it will become a finished item.