Action View serves as the presentation or view layer of the MVC (model view controller) pattern. This means that it’s the component responsible for handling the presentation details of your Rails applications. Incoming requests are routed to controllers which, in turn, render view templates. View templates can dynamically create presentable output based on data structures available to them via their associated controllers. It’s in this dynamic presentation that Action View really helps to separate the details of presentation from the core business logic of your application.
Rails ships with three different types of view templating systems. The template engine that’s used for a
particular request is determined by the file extension of the template
file being rendered. These three templating systems, and the file
extensions that trigger their execution, are: ERb templates (*.rhtml),
ERb templates are most commonly used to generate the HTML
output of a Rails application; they are also used to
generate email messages (though I won’t discuss that until Chapter 9, Action Mailer). They consist of
files ending with the .rhtml file extension. ERb
templates contain a mixture of HTML and plain text along with special
ERb tags that embed Ruby into the templates, such as
<% ruby code %>,
<%= string output %>,
<%- ruby code (with whitespace trimmed)
-%>. The equals ...