Here are the packages with brief descriptions (if available):

[detail level 12]

▼NModIO
CBuildSettings	Build-specific configuration values.
CCreationToken
CDownloadReference	Used in ModIOUnity.DownloadTexture() to get the Texture. (DownloadReference is serializable with Unity's JsonUtility)
CInstalledMod
CModfileDetails
CModId
CModIOUnity	Main interface for the mod.io Unity plugin.
CModIOUnityAsync
CModPage
CModProfile
CModProfileDetails	Use this class to fill out the details of a Mod Profile that you'd like to create or edit. If you're submitting this via CreateModProfile you must assign values to logo, name and summary, otherwise the submission will be rejected (All fields except modId are optional if submitting this via EditModProfile)
CModStats
CProgressHandle	A ProgressHandle can only be used to monitor the progress of an operation and cannot be used to cancel or suspend ongoing operations. The OperationType enum field specifies what type of operation this handle is for. The Progress field can be used to get the percentage (0.0 - 1.0) of the progress. The Completed and Failed fields can be used to determine if the operation is complete and whether or not it failed.
CReport	Used in conjunction with ModIOUnity.Report() to send a report to the mod.io server for a specific mod.
CResult	Struct returned from ModIO callbacks to inform the caller if the operation succeeded.
CResultAnd	Convenience wrapper for essentially a Tuple.
CSearchFilter	Used to build a filter that is sent with requests for retrieving mods.
CServerSettings	Describes the server settings to use for the ModIO Plugin.
CSubscribedMod
CTag
CTagCategory
CTermsHash
CTermsOfUse
CTermsOfUseLink
CUserProfile