The invisible container is a DNN container extension which is: invisible. 

This means, that any module in this container will show only the module, and there is no visible box around it or title above the module. It's usually used in modern web sites where designed content controls if titles are needed and what they should look like. 

To install it, do the following:

1. Download the latest installable package from the releases how
2. Install it like any extension in dnn
3. Usually you will now want to apply it to the whole site (but maybe not - you decide)