Cleric

Clerics serve deities or holy causes of any kind, be it one single entity or an entire pantheon, or someone / something different altogether. Generally a Cleric's work refers to a pantheon of some sort, which in turn is based on culture. A Cleric can thus be described as a servant of (some kind of) culture.
Every deity or divine power has a "Domain," a word that translates into the area of Power represented by that deity. In game terms, it translates into specific powers that the Cleric has---given by their deity--at their disposal.
As you begjn to play a Cleric, access the rules for Domain powers, either in the Core Rulebook (PF2e) or the The Player's Handbooks (v3.5 or 5e). Information can also be found on line. Generally a Domain simply grants one special power, and an extra spell from the Domain.
A Cleric generally does the bidding of their deity, and they strive to live out the deities values and motives in all they do. The divine grants the Cleric magic each day, in the form of Divine Spells.
Clerics can be priests, or filling some role as such, but they can also be crusaders in their deity's name, or in support of their cause, or to spread the word of their greatness one way or another.
The way to the Cleric will match the way of the Deity.

HERE ARE THE PLAYER CHARACTER ATTRIBUTES of the CLERIC (will also need a deity/divine power and a Domain):

• Pathfinder 2e: Core Rulebook or https://2e.aonprd.com/Classes.aspx?ID=5
• D and D v3.5: Player's Handbook or https://2e.aonprd.com/Classes.aspx?ID=5
• D and D 5e: Player's Handbook or http://dnd5e.wikidot.com/cleric

And a list of Clerics / Pantheons / Deities and their Probable Domains:
Dwarven Clerics and List of Deities and Domains
The Deities of the Old Religion of Brahainne, the Drakkaa: "Drakkaa"-- Old Religion of Brahainne
Elven Deities: Elven Deities and Divinities
Gnomish Religion and Deities: Gnomish Religion 
 
If there are no Deities, or Deities without descriptions and/or domains, make sure to consult with your GM to figure it out!