Types of Junglers
Junglers in league of legends often are the ones to alter their choice of character to fit what the team needs most. Depending on what type of composition your team plans on running, you'll end up chosing one of these basic subcategories of Junglers; AD, AP, Tank, and Support. Each of these roles serve a strictly different purpose and before you pick a specific champion, you should first understand what role you wish to accomplish.
AD
Short for attack damage, this role focuses on being one of your team's main damage roles. This is often the best choice to play if your team is very tanky in nature and or is running a large amount of magic damage. This role utilizes items that maximizes their attack damage dealt to the enemy, while generally sacrificing health and defenses to make this possible, such as Shaco would. Depending on how much attack damage your team needs, this role can also serve as a bruiser, building a mix of damage and survivability, such as Vi would. Invading the enemy jungle early and securing as many kills as possible to boost your effectiveness should take priority for this role.
AP
Short for ability power, this role focuses on dealing large amounts of magic damage, whether sustained or burst. This role is best chosen with an AD heavy team, such as if your team is composed of an AD or tank top, AD mid, with a generic ADC. This role utilizes items that will increase their magic damage dealt, often going for a more mixed stat build, including items such as a Rylais Crystal Scepter and Liandrys Torment, as Elise would use. If the team does not need an AP carry, an AP tank would also work well, including Gragas or Zac.
Tank
The tank role is best suited for teams with heavy damage roles already in place, especially if the support is a damage role as well, such as Zyra or Brand. Tanks are meant to do just that, tank or absorb damage from the enemy so their less defensive allies do not take the hit. Focusing on pure defensive stats, tanks build for a combination of armor, magic resist, and health, generally ignoring common damage items to be able to survive for as long as possible in fights. This role seeks to assist allies, generally not prioritizing securing kills, and typically acts as the team's initiator.
Support
The support role is also just that, meant to support the rest of their team with heals, shields, or heavy crowd control abilities. This role is unique because it acts as a second support, prioritizing items to increase healing and shielding, and increasing both offensive and defensive stats somewhat evenly. This role prioritizes keeping enemies away from key allies and keeping said allies healed and protected from surprise threats.