Currently using SP2013 on-prem and need to pull information from and in house application and display it on a page. Not using an iframe how can I pull specific information from a database and feed it into SharePoint. Is there a way to tell SharePoint to allow specific information to pass through? We want to keep this secure also. I'm a front end developer, so this isn't my specialty.
Pulling information out of a database is going to require back-end code.
Anything more specific than that is going to require some knowledge of the external application and your infrastructure in general.