Here are some useful information sources about Russian Orthodoxy:

History of the Russian Orthodox Church:

en.wikipedia.org/wiki/History_of_the_Russian_Orthodox_Church

en.wikipedia.org/wiki/Russian_Orthodox_Church

Orthodox Wiki:

orthodoxwiki.org

The Great Feasts or major celebrations:

orthodoxwiki.org/Great_Feasts

Fasting calendar and description:

orthodoxwiki.org/Fasting