name for concept of a dictionary of most significant words?

I'm interested right now in learning more about the research done on the minimum amount of words needed to speak a language. I know as a concept this stuff exists - I remember seeing this stuff in like an intro linguistics class at university - but I'm not even sure how to phrase it in order to learn more on wikipedia.

A simple frequency list isn't a bad start, but it has a lot of downsides as well vs. something that would be more editorialized by linguistic experts. E.g. there are too many ties (in terms of frequency), too much emphasis on deriving these lists from the written language (often very different from how people speak), and maybe the word selection isn't balanced enough for like an "MVP for communication"

If anyone knows what this concept is called, then I would be able to search for that dictionary for each language I'm interested in, or just learn more about the research that has been done in this area. Thanks!