Other Content Blocks
There are a variety of different types of Content Blocks in this page.
Here's a video from Wistia that I have inserted into the page using a Video Block.
How to adjust the focal point in your Squarespace Gallery thumbnails:
Embedded Content from Third Party Site
Over on the right you will see a poll that I have embedded into this page from Polldaddy. You can embed stuff from lots of third-party websites: pretty much any website that provides embed code. Sometimes you might have to look around in order to find the embed code on the third-party site: if you don't see the word Embed, try looking under Share.
Once you have the embed code, all you need to do is insert an Embed Block into your page, and then paste the code into the block. This is a good way to add functionality to your Squarespace website. It's better than simply linking to the external site because it keeps your visitors on your site instead of sending them away somewhere else.