Effect Monsters

Effect monsters are a kind of Monster card in the TCG and HCCG. They are the most common type of monster in the game. They are color-coded orange. All Toon, Spirit, and Union monsters are considered Effect monsters, and Gemini monsters that have been Gemini Summoned are treated as Effect monsters for the remainder of the duel. There are some Fusion, Ritual, and Synchro monsters which have the "Effect" subtype, but they are color-coded their own respective colors.

Effect monsters are very useful because they each have an effect that activates when certain conditions are met. The different types of effects are listed below:

Ignition Effect Monsters
Ignition Effect monsters have effects that their controller can activate on his/her turn only. Some of them can only be activated upon fulfilling certain conditions, some can only be activated by paying a cost, and some have limitations of when they can be activated. Activating an Ignition Effect is Spell Speed 1.

Trigger Effect Monsters
Trigger Effect monsters have effects that activate in response to another action that just occurred in the duel. Some of them are optional and the monster's controller can choose whether or not to activate the effect, while others are mandatory and must activate at the given instance. A Trigger Effect is activated as Spell Speed 1.

Flip Effect Monsters
Flip Effect monsters are a special kind of Trigger Effect monsters whose effects activate when they are flipped face-up (from being Set). They each contain the phrase "FLIP:" before their Flip Effect. A Flip Effect is activated as Spell Speed 1.

Continuous Effect Monsters
Continuous Effect monsters have effects that remain active while the monster remains face-up (with few exceptions). These effects do not start a chain and thus cannot activate.

Quick Effect Monsters
Originally known as "Multi-Trigger Effect monsters", Quick Effect monsters have effects that their controller can activate on either player's turn in response to another action that occurs in the duel. These effects can be activated as Spell Speed 2.

Special Summon Monsters
Special Summon monsters do not have effects that are activated, per se. Rather, they have conditions that allow them to be Special Summoned in unusual ways. Some of these monsters, known as Nomi monsters, can only be Special Summoned and cannot be Normal Summoned or Set.

To see a list of Effect monsters in HCCG, see this page. Note that some monsters, especially newer ones, have multiple effects and thus can fall into more than one of the above categories.