There are two types of weapons that you can equip to your Hunter, right and left-handed.
Right-handed weapons are your primary weapon and although you can equip two, you can only access one at a time by hitting right on the D-Pad. These weapons are called trick weapons and have two forms of attack that can be changed by hitting L1.
You can also equip two left-handed weapons, which can be switched by hitting left on the D-Pad, and can be either a firearm, torch, or shield. While torches are great for exploring dark area, the firearm will be your primary weapon and is great for ranged attacks and staggering enemies.
Weapons have basic stats that can be increased by fortifying your weapons with upgrade materials or by adding gemstones. In order to upgrade your weapon you’ll need to head to Hunter’s Dream and approach the workbench next to Gehrman to select "Fortify Weapon". Each upgrade requires a certain type and number of upgrade materials and a certain amount of Blood Echoes.
|+1||3 Blood Stone Shards|
|+2||5 Blood Stone Shards|
|+3||8 Blood Stone Shards|
|+4||3 Twin Blood Stone Shards|
|+5||5 Twin Blood Stone Shards|
|+6||8 Twin Blood Stone Shards|
|+7||3 Blood Stone Chunks|
|+8||5 Blood Stone Chunks|
|+9||8 Blood Stone Chunks|
|+10||1 Blood Rock|
In addition to upgrading your weapons you can also equip Gemstones, once you obtain the Blood Gem Workshop Tool, by approach the workbench next to Gehrman to selecting "Blood Gem Fortification". Each weapon takes different types of Blood Gems, with the number of gemstones depending on the weapon, and can attached anything from Physical ATK to adding Poison to your attacks.
Attire is the armor you wear in your clothing slot: Head, Chest, Gloves, and Legs.
Each piece of gear will effect your overall defense either positively or negatively, but some will also effect your resistances to things like Poison and Frenzy. While armor was a pretty big deal in the Souls series, attire in Bloodborne barely effects your stats and is more for aesthetic reasons outside of the resistances.
There are three types of items: Consumables, Arcane, and Key Items.
Key Items are items that you can no accessed for use and are primarily quest related items, such as keys or Messenger Skins. Consumables and Arcane items are those that you can be used, either from the main menu or by equipping them to your hotkey bar. These are often used as offensive purposes, such as throwing a Molotov Cocktail at an enemy, or as support items to cure Status Effects, such as an Antidote to heal Slow Poison and Rapid Poison.