Fairy monsters usually represent beings of LIGHT such as sprites or angels. Many times, the effects of Fairy monsters involve some restoration of the player's Life Points.
They are at a disadvantage when "Yami" is on the field, though fairies do have their own Field Spell Card, "The Sanctuary in the Sky". Plus many gain a 500 ATK point boost from cards such as "Luminous Spark", "Rising Air Current" or "Gaia Power" because most Fairy monsters are either LIGHT, WIND, or EARTH Attribute (and in a few cases, DARK and WATER Attributes too.)
The Agent and Archlord cards of the Ancient Sanctuary series are perhaps some of the best-known Fairies and some possess good effects. Union monsters "Aitsu" and "Koitsu" work very well together as a low-level union with a high ATK, as do "Soitsu" and "Doitsu". "Cloudians" are a Water attribute but share the fairy sub type, they "The Sanctuary in the Sky" in their main gameplay. The Majestic Mechs are also a very good breed of Fairies.
One of the best-known Fairy archtypes are the Synthetic Angels, who have effects revolving around the use of Counter Trap Cards. Bountiful Artemis and Voltanis the Adjudicator are examples of this. This archtype was featured prominently in the OCG Structure Deck Structure Deck 11: Wave of Flashing Light.
In the OCG, Fairies are called Angels.