Units
Intro 
Currently there are a handfull of types of units.  You can see the sprites for several of the unit types here.  Each unit is composed of elements so your civ's phalanx unit can be different in capabilities form those of your neighbors (creating cusom units is however not yet supported in demo 5).  The idea of elements also allows Clash units to have true combined-arms capabilities in a natural way. If you want to learn more, you can check out the Units spec.  The element composition of the units is given below.
 
Land Units
The available land units are: Warriors; Phalanx; Light Cavalry; Horde; and Chariots. You can see the first three types listed in the graphic above.  They are composed of the following elements for now (playtesting or more discussion could change these easily, number of the element type is shown after the element name):

  WarriorBand is made of: Warrior 9, and Skirmisher 1
  Phalanx is made of:  HeavySpear 5, LightSpear 3, and Skirmisher 2 
  Light Cavalry is made of: Charger 3, and CavalrySkirmisher 6 
  Horde is made of:  Warrior 8, and CavalrySkirmisher 2 
  Chariots is made of:  Chariot 10

Movement rate and combat power depend on the element composition of the unit, and whether elements within the unit have been damaged or destroyed.  As you might expect the Light Cavalry moves more rapidly than the others on flat ground.

For the curious, here is an example of the current element spec:

- <Element>
  <Name>Warrior</Name> 
  <Default>null</Default> 
  <category>foot</category> 
  <Attack>20</Attack> 
  <Defense>20</Defense> 
  <Movement>35</Movement> 
  <Distance>5</Distance> 
  <Armor>2</Armor> 
  <Health>1</Health> 
  <Morale>8</Morale> 
  <Mobility>4</Mobility> 
  <Order>Attack,Garrison</Order> 
- <Cost>
  <Food>0</Food> 
  <Production>6</Production> 
  <Services>1</Services> 
  <Decay>0.03</Decay> 
  <Training>1</Training> 
  </Cost>
  </Element>
 
Naval Unit -- Trireme
The Trireme is just in there for show right now.  You can build them, in fact without a requirement for there being water nearby!  With Demo 6 we will hopefully have rules for naval combat and transport.