For information on areas of research in the field of communication, check out the National Communication Association's page, "What is Communication:" https://www.natcom.org/about-nca/what-communication.
What's the difference between a database and a journal? A database is a collection of journals, so when you're searching a database you're going through a large amount of articles from various journals. Journals are focused on specific topics or approaches to subjects.The journals listed here are leading titles in the area of Communications.
For information about current trends in the field, you can check out Communication Currents, an accessible publication from the National Communication Association that presents academic trends for a broad audience.