bogdan

Embeds are needed to embed video from youtube or to embed Google Map or just to embed content from external page. 
WordPress removes embed when you switch from “HTML” to “Visual” tab because of the security reasons. 
So you can embed object code using this shortcode <code>[iframe src="http://player.vimeo.com/video/3261363" width="100%" height="480"]</code>.

iframe to embed

Embeds are needed to embed video from youtube or to embed Google Map or just to embed content from external page.

brajesh

Embed Iframe is a plugin that will let you embed iframe – an HTML tag that allows a webpage to be displayed inline with the current page, in a WordPress post. Although an iframe can lead to a complicated website, it can be very effective when used appropriately.
<h3>Usage</h3>
Use following tag to insert another page in post using iframe
<pre><code>[iframe url width height]
</code></pre>
e.g.
<pre><code>[iframe http://www.example.com 400 500]
</code></pre>

Embed Iframe

Allows the insertion of code to display an external webpage within an iframe.

iframe to embed vs Embed Iframe