iFrame is an HTML element that allows you to load another web page into your page. For example if you have an HTML page and you want to embed a YouTube video, you would put in a code like this:
<iframe width="560" height="315" src="https://www.youtube.com/embed/n_O1B_2tAlk" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" allowfullscreen></iframe>
If you want your bubble page to be embedded in a customer webpage as a component, they can call your page with and iframe <iframe src="https://yourpage.com"></iframe>
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For that to work efficiently there are things you need to do. Firstly you must allow iFrame in the settings. More generally you need to design your page for iFrame this means thinking about the size of the page, thinking about URL parameters and slugs, thinking about how you are going to send and receive events from the parent page (if needed), etc…