How does the goal difference work?

You find the Goal Difference (GD) by taking away the goals conceded from the goals scored e.g. in a match the home team scored 2 goals but let in 3, (2-3) their goal difference would be -1, and the away team's GD would be 1 as they scored 3 goals and let in 2 (3-2) If 2 teams are level on points in the league table, if the 1st has a GD of 5 and the 2nd has a GD of -3, the 1st would be above the 2nd. Sorry if this is confusing.