There are different warriors in Celtic Tribes. The slinger is available from the start, whereas the other warriors can be enable by researching runes. The units are basically divided into several categories. Here is an overview of those:

Name: Slingers 

Type: Artillery

Strength: Offense 

Name: Archers 

Type: Artillery

Strength: Defense 

Name: Spearmen 

Type: Infantry

Strength: Defense 

Name: Axe fighters 

Type: Infantry

Strength: Offense 

Name: Lancers 

Type: Cavalry

Strength: Offense 

Name: War chariots 

Type: Cavalry

Strength: Defense 

Name: Catapults (Fortress)  

Type: Cavalry

Strength: Offense 

Name: Ballistas (Fortress)    

Type: Infantry

Strength: Defense

Name: Rams (Fortress)    

Type: Artillery

Strength: Offense 

Name: Handcarts 

Type: Transport

Strength: Transport 

Name: Ox carts 

Type: Transport

Strength: Transport 

Name: Druids 

Type: Conquest

Strength: Conquest