https://s4be.cochrane.org/blog/2021/04/06/main-databases-for-literature-search/
This is from a site called "Students 4 best evidence" and provides a description of some of the databases available - some free, some by subscription only - their focus, and when to use them.
Evidence Synthesis Ireland provide a range of very useful webinars - free. Check out their forthcoming events at: Training and Webinars • Evidence Synthesis Ireland