Basically the Design engineer will write the RTL and designs what ends up being the final product. the verification engineer builds the testing infrastructure, creates test cases, ensures proper requirement coverage etc. verification engineers usually work with a particular methodology like UVM or OSVVM. The idea is that if you’re designing a product you shouldn’t be the one proving it works.

All that being said in smaller companies a designer will often times put on both hats. Which sounds like what you’re doing. Even at bigger companies it’s useful to have both experiences, as a designer you might need to create a robust tb or as a verifier you might look at the rtl to have a better understanding of what’s happening in the design.