From Learn About the Ext JavaScript Library

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Main data concepts

• Stores - Store is the backing store of the Grid. It is a cache of Ext.data.Record objects which contains the fields you specify. The fields may be accessed by name.
• Proxies - The Store uses a Proxy object to pull the data in from wherever it may be. If you just have an in-page javascript array, it will be a MemoryProxy whose constructor just takes the data. If you are pulling the data from a server on the same domain it will be an HttpProxy. The Proxy is fairly dumb. It just provides access to a blob of data. You specify a Reader object depending on the type of data that is being pulled in. So an XmlReader if you are pulling in an XML document using an HttpProxy. You'd use an ArrayReader if you just had a MemoryProxy which wrapped an Array of values.
• Readers - The Reader, being given your Record definition in its constructor, knows the "mapping" of each field, ie a reference that enables it to pull the required data out of the blob. It pulls the individual fields out of the raw data blob and populates an Array of Records which are passed back into the Store's loadRecords method which updates the Store's cache.

Base data classes

• Ext.data.Connection (doc) - The class encapsulates a connection to the page's originating domain, allowing requests to be made either to a configured URL, or to a URL specified at request time.
• Ext.data.Record (doc) - Instances of this class encapsulate both record definition information, and record value information for use in Ext.data.Store objects, or any code which needs to access Records cached in an Ext.data.Store object.
• Ext.data.SortTypes (doc) - This class is a singleton and cannot be created directly.
• Ext.data.Tree (doc) - Represents a tree data structure and bubbles all the events for its nodes.
• Ext.data.Node (doc) -