When is a throw-in awarded in a soccer match?

A throw-in is awarded when the ball goes out of play over the touchline, which is the line that runs along the sides of the field. This situation occurs when the entire ball crosses the line, either on the ground or in the air, last touched by a player from the opposing team. The purpose of the throw-in is to resume play, allowing one team to throw the ball back into the field from where it exited.

The other options are not correct because they pertain to different rules and situations in the game. The goal line is involved in awarding different types of restarts, such as a goal kick or corner kick, but not a throw-in. Substitutions and offside violations have their own specific processes and rules that do not include a throw-in as a form of restart. Thus, the correct answer clearly defines the scenario in which a throw-in is applicable within the rules of soccer.