Top laners are champions (or the players of those champions) that tend to spend the lane phase farming in the Top Lane, though sometimes teams will swap their lanes, so the top laner will be in the Bottom Lane. Top laners tend to be self-sufficient champions during the lane phase, not needing significant help from another champion to stay alive. There are two main styles of top lane champions: tanks and carries. Tank top lane champions generally try to soak damage from the enemy backline while their own backline kills the enemy frontline. Carry top lane champions generally try either to splitpush or to carry fights for their team as if they were a mid lane mage. Examples of top lane champions include: Ornn, Sion, and Cho'Gath (tanks); Aatrox, Gangplank, Jayce, and Rumble (carries); and Urgot, Gnar, and Jarvan IV (balanced champions).
For information about common top lane item builds, see: here.
Junglers are champions (or the players of those champions) that spend the early game in the jungle clearing camps and/or ganking lanes. Junglers will always run the Smite summoner spell, allowing them to clear their jungle faster and also to secure last-hits on Dragon and Baron for their team. Junglers usually don't get as much gold income as top laners, mid laners, or AD carries, and so they tend to build more support-oriented items that help their team. Junglers frequently function as the primary initiator of fights, though that is not always the case. Champions played primarily in the jungle include Gragas, Sejuani, Olaf, Trundle, Skarner, and Kindred.
For information about common jungle item builds, see: here.
Mid laners are champions (or the players of those champions) that spend the early game in the middle lane. There are three classes of mid laners: mages, assassins, and utility champions. Mages and assassins rely primarily on their spells to do damage, but mages are geared more towards teamfighting, while assassins want to pick someone off and instantly kill them. Utility mid laners behave similarly to supports and will usually try to help their team survive in fights. Mid laners will often be seen roaming to the side lanes or even into the jungle once they hit level 6 and have a point in their ultimate, but they will typically prioritize farming for the most part. As such, mid laners tend to have fairly high waveclear, though that is not always the case. Mage-oriented mid laners include Ryze, Syndra, Cassiopeia, and Orianna; assassin-oriented mid laners include LeBlanc, Irelia, and Akali; and utility-oriented mid laners include Karma, Malzahar, and Zilean.
Mid lane is by far the most diverse role when it comes to summoner spell choices. There are a variety of viable summoner spells for mid laners, like Ignite, Ghost, Cleanse, Heal, Barrier, or Exhaust. Sometimes, mid laners will run the Teleport summoner as a more strategic option. Any of these summoner spells can be combined with the traditional choice of Flash
For information about common mid lane item builds, see: here.
Bot laners are champions that are often ranged and tend to spend their time in the bottom lane with a support helping them secure farm and stay alive. Bot laners often play "marksmen" (also known as AD Carry) champions that are very fragile and easy to kill if caught alone yet very destructive, especially in slower pace games and longer ones as they represent the biggest output of damage in the late game. Sometime, they are swapped for mages or other roles depending on team composition. Usually at least one member of the team will be devoted to keeping enemies away from the Bot laner in fights; this is referred to as peeling. Popular bot lane picks include Kai'Sa, Varus, Xayah, Tristana, Ezreal, Heimerdinger, Yasuo, and Swain.
For information about common bottom laner item builds, see: here.
Supports are champions (or the players of those champions) that generally aren't allocated team resources (lasthits/kills) and instead provide team utility with a very limited income. They tend to have multiple forms of CC or other utility as their spells, and so are able to be effective without building expensive items to make their spells do more damage or to make themselves harder to kill. Instead, supports typically buy an item that gives them additional gold income and frequently several items that have activatible effects that provide utility. Supports are responsible for a large portion of their team's vision control. In teamfights, a support's goal is usually either to peel for their ADC, to lock down the enemy backline, or a combination of the two. Popular support picks include Braum, Tahm Kench, Alistar, Rakan, Shen, Pyke, Morgana, and Thresh.
For information about common support item builds, see: here.