Discovery Findings
The main outcome from discovery is the learning by doing the discovery. This outcome is more important than the output of documents.
There will be some document outputs however. They'll depend on which discovery modules were undertaken, but the following will be the most common:

Personas

We start to build concise descriptions of the users of the service based on the research during discovery. These typically include clear goals, motivations, and contextual information that helps us think from their point of view when making decisons.

User needs

The high level goals, motivations, or problems to solve of the (potential) users of the service. Good user needs are based on something a real user would say, and would avoid implying a solution.

User journey maps

A breakdown of the steps needed to achieve a user need. This helps us breakdown the work involved and includes any contextual information that helps us design solutions.

Stakeholder maps

A clear idea of who has a stake in the project, their impact on the project and identification of who should be engaged with in further stages of the project.

User Stories

These are written in the format of user stories.

Risk map

A view on the key risks to the project, their likelihood and potential impact — and suggestions for how to mitigate them.

Recommendations for proceeding

This will include suggestions for the scope, duration and budget range for a prototyping phase. It is also valid for a discovery phase to result in a recommendation not to proceed, or to recommend another discovery phase looking in a different direction.