In Football, When Is an Offside Player Considered to Be Interfering With Play?

I understand that being in an offside position isn’t automatically an offence, but the “interfering with an opponent” part still feels hard to judge. A forward can be standing near the goalkeeper without touching the ball, and then a goal is ruled out because they were affecting the play.

What are referees and VAR actually looking for in those situations? Does it depend on whether the player blocks the keeper’s view, challenges for the ball, or changes a defender’s movement? A clear example from a match would help make the distinction easier to follow.