expressionengine vs codeigniter

[eluser]Eduzinho[/eluser]
Please take into account I have experience with PHP, but I am not very skilled in CMS or frameworks.

So I understand that when we talk about integration of CI and EE, we refer to developing EE add-ons written with CI. Is this point of view correct? But is this the only way to communicate parts of an application in CI with EE? Is there any other possibility? In short, as I want to be able to code outside of the CMS, can I connect CI and EE this way?

Sorry for my English, I think my other posts could not be very clear. I think it is much more difficult for me to progress with these doubts, and I didn't find community articles or Google search results to solve them so far...

Thanks again