I am new to FileMaker, but interviewing for a position working with it.  They are aware that I am new, but I want to be able to demonstrate that I have done my research.  Can anyone help with topics that I should be familiar with?  I have been a developer and database guy for a couple decades, so looking for FileMaker specific knowledge.

I'd recommend attempting to learn the terminology first. Some of it would be familiar enough to you (tables, records, layouts, scripts, etc.) others might not be (table occurrences, relationship graph, view modes). You can probably get that from the manual: https://fmhelp.filemaker.com/help/18/fmp/en/#page/FMP_Help%2Fsolutions.html%23

Since you're already a developer, I'd say understanding what's unique about FileMaker would be the next most helpful. Off the top of my head, I'd say some of the big ones are:

• context: everything in FileMaker is accessed through the relationship graph, where each base table can occur 0 to many times and be related (or not) to other table occurrences. A layout is based on a table occurrence, which provides it's context in which it accesses related data. Scripts run from the context of a layout (but you can change layouts in a script, to get a different context).
• development and deployment platform: FileMaker is an IDE, client app, server app, web app; it does it all.

Just browsing the chapter headings Dan linked should give you a good idea:

https://fmhelp.filemaker.com/help/18/fmp/en/

I'd agree platform is important: WebDirect, Custom Web Publishing (CWP), Data API, FileMaker Go.

Security is on the radar of most companies these days. Get familiar with FileMaker's security model, including all the options of the Security dialog, encryption at rest (EAR), and field-level encryption.

You should be aware of developer tools that are out there, such as BaseElements, FMPerception, plugins, etc.

I still recommend the FileMaker Training Series book -- even though it hasn't been updated since version 15, most of it is still applicable:

https://community.filemaker.com/en/s/article/free-filemaker-training-series--advanced-for-filemaker-15

and then you can supplement with what's new, e.g. Card Windows:

https://www.filemaker.com/products/filemaker-pro-advanced/version-comparison.html#fm16

Welcome to the forums!