Finders assist you with often-used database queries so you don't have to write them over and over again. Out of the box, Lithium provides you with a bunch of them: all, first, count list and "magic finders like" findById or findFirstById. How these are constructed in the core is not relevant for now, but Lithium provides you with a mechanism to write your own finders easily.
He starts with a look at the bundled finder, showing how it uses a _findFilters method to create the default filter and pass it into your configuration. He covers the parameters you'll need to define and an example of making a Task to create a new one. His example sets a limit of five results on the response. He also mentions the ability to add a custom finder to your model, loaded in the _init() automatically.