Raduraksti is a crucial resource, the Holy Grail of Latvian genealogy, should you wish to research your family tree. Hosted by the Latvian State Historical Archives, it contains multiple types of records, and more are being added all the time. They are mostly digitized copies of original documents. The documents I use more than any other are the church books – baznicas gramatas.
The church books are typically birth/baptism, marriage and death/burial (BMD) records from churches all over Latvia. They are organized by religion, then parish. The most common religion in Latvia, Lutheran church books records are in German and Russian, depending on the time period. German is close enough to Latvian to understand names, and the Russian text usually has first names and surnames spelled out in German as well. The church books only have records up until 1909, and it is important to note that there are gaps in their coverage, as some books have been lost or destroyed.
Records you find on Raduraksti may be hard to understand for the English-as-an-only-language researcher such as myself, since are in old-German script, Russian Cyrillic, Russian translations of German translations of Latvian names and places, etc.
Here’s an excellent guide to beginning to understand these records: http://www.celmina.com/genealogy/2011/09/anatomy-of-a-birth-record/