Many propositions in number theory concerns about the existence of primes of a certain form. Some of them has been proved to be true, such as for $x$ (Euclid's theorem), $4x+1$, etc.; many others remain conjectures, such as for $x^{2} + 1$ (one of the Landau's problems).
A common characteristic of the examples presented above is that the "forms" are all polynomials. One can then ask the more general question: what is the set of "polynomials forms" for which there are infinitely many primes of? In other words, given a random polynomial, how can we tell if infinitely many prime numbers of that form exist?
I am quite sure that this thought has been investigated before since this question is quite natural to ask, but I was not able to find any descriptions of this problem online. Could someone provide some existing approaches, or resources in general?
P.S. I must say that I am an only an amateur on this topic, and do not know about the proper terms professionals use to describe the above-presented vague/awkwardly-stated ideas such as "any polynomial form" or "infinitely many". I would appreciate anyone who would provide a better statement of my thoughts presented above, with which the internet researches could become much more effective.