Builder is a reference to a Milo builder.

Console is a waterfall definition consisting of one or more builders.

ConsoleSummaryGroup is a list of consoles to be displayed as console summaries (aka the little bubbles at the top of the console).

Header is a collection of links, rotation information, and console summaries that are displayed at the top of a console, below the tree status information.

Link is a link to an internet resource, which will be rendered out as an anchor tag <a href="url" alt="alt">text</a>.

LinkGroup is a list of links, optionally given a name.

Oncall contains information about who is currently scheduled as the oncall (Sheriff, trooper, etc) for certain rotations.

Project is a project definition for Milo.

Settings represents the format for the global (service) config for Milo.

SourceAcls grants read access on a set of Git/Gerrit hosts or projects.