What the definition of validity of a formule in a possible Kripke-world in Modal Logic?

Question

Basic question here but I cannot find the definition:

Given a modal logic and a set of propositions $P$, a model $M=(W,R,V)$ where $W$ are possible worlds, $R$ an accesibility relation and $V$ a valuation for every $p\in P$

What is de definition of $(M,w)\models \varphi$?

And whats the name of it? Validity?

Thanks