How can i know the relationship in the database in sql server 2008? [on hold]

I want to know how can I determine relationships between data which is not determined by the primary key in the design.

For example, I have three tables in the database like this :-

table 1: fields 
table 2: area 
table 3: location

All of the tables have data but the person who created the database did not explain the primary keys and the foreign keys in it. How can I know the relationship between these tables?