Hybrid refers to using two or more champion build types. These combinations can be beneficial, and can allow a champion to be more diverse in terms of its combat effectiveness.
Forms of Hybrids
Typically there are different types of how the term Hybrid can be thought of.
Attack Damage | Ability Power Hybrid
This is the common form. Champions of this category usually build both AD and AP in order to be effective.
Noteworthy AD/AP Hybrids:
Common items used:
On-Hit / Attack Speed Hybrid
These champions utilize attack speed and on-hit effects in order to be lethal in combat. They often also scale well with ability power and benefit more from magic penetration than armor penetration, due to most on-hit effects dealing magic damage except 
Blade of the Ruined King.
This Hybrid form is best on champions like:
Bard- Braum
- Diana
- Fizz
- Janna
- Kayle
- Kai'Sa
- Kennen
- Kog'Maw
- Lulu
- Shyvana
- Teemo
- Twisted Fate
- Varus
- Warwick
Common items used:
- Nashor's Tooth
- Guinsoo's Rageblade
- Wit's End
- Blade of the Ruined King
- Runaan's Hurricane
- Sorcerer's Shoes
- Berserker's Greaves
Other
Other Hybrid forms are champions that can be built either AD or AP, but tend to be underwhelming if mixed. They should specialize in either Attack Damage or Ability Power.
Champions like:
