Troops are the units led into battle by your dragons. They are used to battle against other players and PvE monsters. 

How do I train Troops?

You can train Troops using Food in the Training Pit on the City Map.
You can unlock higher level troops via the research in the University.

What types of Troops are there?

There are currently four tiers of troops, often referred to as T1, T2, T3, T4.

Tier 1 = Militia 

Tier 2 = Guards

Tier 3 = Pug Riders, Knights, Huntresses

Tier 4 = Wild Pugskateers, Royal Knights, Trophy Huntresses

Tier 3 and tier 4 troops have 3 type of troops, each good at one specific thing (attacking in PvP - Pug Riders/ Wild Pugskateers, defending in PvP - Knights/ Royal Knight  and attacking monster - Huntresses/ Trophy Huntresses). 

Troop research can further upgrade their power (attacking = strength and defending = toughness) along with other upgrades like march speed