Most range attacks are direct attacks aimed at a specific person. Weapons such as grenades or mortars are not used in this way. They are aimed at a location, normally a 5' square, and rely on a blast or similar effect hitting everyone in the area. These are indirect attacks.
An indirect attack is a standard action resolved exactly like a direct attack. However because indirect attacks are made against a location the resistance for the attack is generally set by situation bonuses for range and cover. The Game Leader or another player rolls the resistance in these cases.
Only if someone is in the exact targeted location (i.e. the same square) can they make a resistance action against the attack. As an indirect attack is aimed at a location, the character in the square cannot try to dodge the attack because they are not the target. The occupant can only return fire to distract or hinder the attacker's action by returning fire.
It may be possible for the defender in the square to interfere with the attack, for example using their rifle in the style of a cricket bat to knock a grenade away. Whether this is possible is left to the group to decide based on the situation. Any attempt to do this adds to the resistance against the attack.
Most indirect attacks are associated with cards with the effect keywords. When these go off they make an attack against everyone in the area, provoking resistance actions. As the blast is a separate attack from the original indirect attack, the character in the target square will have a resistance action against this attack.