How many balls before a walk?

I'm curious, could you elaborate on the phrase 'How many balls before a walk' in the context of baseball? It seems to imply a specific rule or sequence of events that leads to a player being awarded a base on balls, also known as a walk. Is there a fixed number of pitches that must be thrown outside the strike zone before a walk is called? And if so, what are the exact conditions that must be met for this rule to be applied? I'd like to understand the intricacies of this aspect of baseball's rulebook and how it affects the game's strategy and flow.