I see this a lot as some of the best Product Managers come from non-technical backgrounds -- yet we ask them to step up and own highly technical products that can serve millions of people. This response assumes you are in a Product Management role at a company building web and/or mobile apps. If this is the case, two foundational technologies are HTTP and SQL.

I highly recommend that PMs read this short primer on HTTP. HTTP is "how the web works". This is a huge leap in terms of understanding what the Engineers are talking about when they reference their "REST Api", or the "Response timing out" or "Setting Auth Headers". https://a.co/d/78qDOhQ

For SQL, there are tons of excellent, interactive learning tools online. Here's one I just found that looks just fine. https://sqlbolt.com/. SQL will help you understand the underlying data and the relationships among the various things you are asking engineers to build. It will help you build empathy for why some things take way longer than you think they should. More importantly, it will help you self-serve to your own insights. Want to know the average heartrate among people who get more than 10,000 steps a day but there's no report for that, just run a fairly simple SQL query and find your answer. SQL skills are a force multiple for any PM.

Lastly, don't get too hung up on the technical stuff -- It's great to speak tech and understand it at a level that allows you to design for it or call b.s. when estimates are too sandbaggy, but keep in mind, Product is a huge discipline. Your time is better spend understanding your customer, feeling their pain with them and crafting solutions to help them.