Do you ever feel like you can't do something? Or that you don't have the skills? Most people do.
It's easy to fall for the idea that you don't know how to do something, even if it seems entirely different from everything else you've ever done.
The content could be different, but the process is often the same. In other words, the 'what' may be different, but the 'how' is often similar. That's where transferable skills come into play.
Suppose you have been a project manager in the finance industry for ten years, but have never worked in logistics. The industries are dissimilar, but fundamentals of project management will remain the same: identify the desired project outcomes and potential challenges; gather the appropriate resources (time, money, technology, people), delegate specific tasks; support the team and monitor the progress.
Nothing in the previous description said anything about finance or logistics, only about the process of project management.
Many serial entrepreneurs understand and use this concept when starting new businesses; they don't have to know much about the industry they're going into (although that doesn't mean it's always a good idea). They just go through the same process as before: market research, business planning, execution and analysis. Then, they harness the advice and guidance of experts in the area and delegate as much work as feasible.
Others who are looking for their passion want to know 'what' they should do with their careers. A person can spend a lot of time trying to figure out 'what' makes them happy, they overlook the fact that it's the 'how' that makes them smile, i.e. being surrounded by supportive people; having opportunities to learn; helping others in some way, etc.
When you want to change jobs, distinguish between the content and the process of your current role. Then, ask yourself if you're more interested in the content or the process, the 'what' or the 'how'.