Thrown weapons are a type of ranged weapons.
Bows and crossbows are also ranged weapons, but normally do not get the strength bonus to damage (however specific bows can be made to get the strength bonus). Other weapons that have ranged attacks that don't get strength bonus include firearms and most ranged touch attacks.
Core Rules p. 179 says for Damage "Strength Bonus: When you hit with a melee or thrown weapon, including a sling, add your Strength modifier to
the damage result."A Javelin is in the "Ranged Weapon" category as has the Str bonus applied.
Are all Ranged Weapons considers thrown for the Str bonus?
What is the difference between Ranged Weapons and thrown?
The mechanical answer to your question, is whether or not the weapon uses ammunition. If it does, as with bows and crossbows, you do not add your str bonus. If they don't require ammunition they are "ranged thrown weapons" and you add you strength bonus to it.
The are a few exceptions to the rule, where ranged weapons (with ammunition) does add your strength bonus, specifically slings and composite bows.
The reason javelin is in ranged weapons despite being a thrown weapon is because it cannot be used as a melee weapon.
EDIT:
A javelin is a thin throwing spear.
Note: Since a javelin is not designed for melee, you are treated as non-proficient with it and take a –4 penalty on attack rolls if you use a javelin as a melee weapon.