Damage type
There are multiple damage types in Rust. Each type has different effectiveness versus various objects depending on the protection.
On the left of the inventory screen, the types of damage and their protection values on the player are visible. From top to bottom: Cold, Heat, Radiation, Falling, Electric, Explosion, Blunt, Slash, Stab, Bullet, Bite.
Bite
This type of damage is caused by hostile animal attacks, specifically bear and wolf also monkeys attacks.
Blunt
This type of damage is caused by blunt weapons, such as the Rock, as well as the Mace (in addition to Stab damage) and the Salvaged Hammer.
Bullet
caused by damage from gunshots (and maybe Wooden Arrows). Regular clothing will not do much to protect one against bullet damage, but it is better than nothing. Armor however, is very effective at protecting against bullet damage.
Cold
Cold damage isn't too much of a problem during the day (unless you live in an arctic or mountain biome), but at night, being too Cold can result in the difference between life and death. It is very easy to avoid being cold. You can either wear an adequate amount of clothing to stay warm, or stay close to a Camp Fire and utilize its Comfort buff. Alternatively, you can stay within a Temperate biome and the temperature will usually still be warm enough for you to avoid taking Cold damage. Even a simple pair of pants is almost good enough to avoid freezing to death on a cold Rust night.
Electric
Electric damage is only used by Code Locks from an incorrectly entered password, and as of Devblog 110 there is no article of clothing or piece of armor that protects against this type of damage.
Explosion
This damage type is caused by explosive weapons and explosions, like the more obvious F1 Grenade, Timed Explosive Charge, Satchel Charge, and Beancan Grenade, as well as Rockets and even Explosive 5.56 Rifle Ammo. There is no specific, very effective counter to explosion damage, but avoiding the blast, as well as equipping armor can save your life.
Falling
Falling damage is what you get when you jump or fall off of a high place, like the roof of a 3-floor building or the top of a rock face. Equipping armor may help protect you against lethal fall damage, at least to a small degree.
Heat
Heat damage occurs when the player steps on a Camp Fire. The Flame Thrower also utilizes heat damage to inflict damage.
Radiation
Radiation damage comes from world-generated structures commonly known as "radtowns". The most effective way of combating this damage is with anti-rad pills, which cannot be crafted but instead found inside Loot Crates. Hazmat Suits can also be worn to prevent radiation damage. Clothing and other armor will protect against radiation to a small degree.
Slash
Slash damage is associated with sharp, usually long weapons like the Machete and Longsword. Weapons with slash damage are usually associated with a bleeding effect after a successful hit to a target. These weapons are often strong against unarmored players, as well as animals.
Stab
Stab damage often come from weapons such as Bone Knives and similar weapons. Just like weapons with high slash damage, these often deal bleeding damage after a successful hit, making them efficient against players without armor.