Structs

Represents authentication helpers provided by Postman
Represents an attribute for any authorization method provided by Postman. For example username and password are set as auth attributes for Basic Authentication method.
Data is an array of key-values that the request goes with. POST data, PUT data, etc goes here.
Defines a script associated with an associated event name
One of the primary goals of Postman is to organize the development of APIs. To this end, it is necessary to be able to group requests together. This can be achived using ‘Folders’. A folder just is an ordered set of requests.
Set of configurations used to alter the usual behavior of sending the request
A request represents an HTTP request.
A script is a snippet of Javascript code that can be used to to perform setup or teardown operations on a particular response.
Collection variables allow you to define a set of variables, that are a part of the collection, as opposed to environments, which are separate entities. Note: Collection variables must not contain any sensitive information.

Enums

A request can have a specific data mode, and Postman supports these.
A Description can be a raw text, or be an object, which holds the description along with its format.
A response represents an HTTP response.
A helper may require a number of parameters to actually be helpful. The parameters used by the helper can be stored in this field, as an object. E.g when using Basic Authentication, the username and password will be stored here.
The host for the URL, E.g: api.yourdomain.com. Can be stored as a string or as an array of strings.
The language associated with the response.
The complete path of the current url, broken down into segments. A segment could be a string, or a path variable.
A request URL may contain one or more path variables (e.g: :varname)
A Postman request allows you to use Path Variables in a request, e.g: /search/:bookId. This field stores these variables.
Contains the raw data (parameters) that Postman sends to the server
A response represents an HTTP response.
The time taken by this particular HTTP transaction to complete is stored in this field. For manually created responses, this field can be set to null.
If object, contains the complete broken-down URL for this request. If string, contains the literal request URL.
A response represents an HTTP response.
A variable may have multiple types. This field specifies the type of the variable.