A content type is a reusable collection of metadata (columns), workflow, behavior, and other settings for a category of items or documents in a SharePoint 2013 list or document library. Content types enable you to manage the settings for a category of information in a centralized, reusable way.

We can correlate Content type with Classes (in OOPs).1. Class and content type both are molds. 2. Class has properties; Content type has site columns. 3. Instance of class is object; Instance of content type is item. 4. Class has behavior defined in a way of functions; Content type also has behavior defined in a way of workflows and event receivers.

ContentType is One Kind Of List .it Contains Site Coloumns. also know Re-Useable template

Content type is a template where you can define meta data like what is the type of the column and what is the behavior, reusable component and it's one of the basic component in SharePoint

Group of Site Columns are content types. We create content types at Site Collection level. They are reusable items.

A content type is a flexible and reusable WSS type definition (or we can a template) that defines the columns and behavior for an item in a list or a document in a document library. For example, you can create a content type for a leave approval document with a unique set of columns, an event handler, and its own document template and attach it with document library/libraries.