Vulnerability is the starting point for every bidding decision. The crux of being vulnerable is that the bonus for games and slams increases, but the penalty for going down also increases, particularly if the opponents double.
There is a misconception that dictates being cautious when vulnerable, but if players are too cautious they can miss out on their game bonus. So a mixture of appropriate aggression and caution is the key.
Part-score battles are also dictated by vulnerability. Being non-vulnerable is the best time to compete aggressively, especially against vulnerable opponents, who should take part-score decisions, particularly on the three level, with some caution and care.
From opening bids to preempts, and everything that follows, vulnerability will change the nature of the game. Understanding the nuanced differences between the four vulnerabilities will give you a big edge.