Elizabeth of
Russia was the daughter of
Peter the Great and his second wife
Catherine I. She was born before her parents were publicly married, and later in her life fought some prejudice from Russian
nobles because she was the daughter of a woman who was born a
Lithuanian peasant. However, Elizabeth was brought up as a
princess; Peter originally hoped to marry her to the son of the
King of
France but this plan fell through, and later to the
Bishop of Lubeck, who died before they could marry.
After Peter died in 1725 and Catherine reigned, Elizabeth was a helper to her mother and gained some familiarity with the issues of government. When Catherine died, she had been persuaded to name her step-grandson Peter II as her heir instead of Elizabeth or her other daughter Anna Petrovna. Elizabeth was a great friend of Peter's, though, and continued to have influence in the country. Peter's death in 1730 could have given Elizabeth an opening to take the throne, as she had the support of the Palace Guards, the nobility, and many of the Russian people. However, the Supreme Privy Council thought she was too frivolous and disliked the descendants of Catherine I, so they chose Anna Ivanovna, daughter of Peter the Great's brother Ivan V. Elizabeth and Anna did not get along, possibly because Elizabeth's independent ways scandalized her court. Anna threatened to have Elizabeth put in a convent, but Anna's lover Biron persuaded her that this would not be a good public relations move due to Elizabeth's popularity.
When Anna died in 1740, she had named her baby great-nephew Ivan VI as heir. In barely a year, though, Elizabeth gathered the support of those who didn't like the number of Germans in power in Russia as well as those who had already liked Peter and Catherine's vivacious daughter. In November 1741, Elizabeth was able to lead her father's favorite guards, the Preobrazhensky regiment, and take power without bloodshed. Ivan was imprisoned -- Elizabeth, a religious woman despite her fun-loving attitude, had sworn never to sign a death warrant -- and his parents were exiled from Russia.
Elizabeth generally wanted to restore things to the way they had been in her parents' time. The major government official under her was her father's one remaining favorite, A. P. Bestuzhev-Riumin, but she called councils to advise her often. Her lovers were often given a lot of power also, but no one could override what Elizabeth was set on. She may have secretly married one lover, Razumovsky (nicknamed "the night emperor" at court) but she never publicly married, citing a broken heart at the death of her earlier fiance. To ensure the succession, she summoned her nephew Peter to Russia from Holstein where he lived with his father, and made him her heir. She also found Peter a wife, the daughter of her late fiance's sister, who was baptized into the Orthodox Church as Catherine. After some years when Catherine finally had a son, Elizabeth took over baby Paul's upbringing and Catherine barely saw her son for the first few years of his life.
Elizabeth tried to keep Russia at peace, even though most of Europe was taking sides in the War of the Austrian Succession and eventually the Seven Years' War -- she was officially on the Austrian side of each but did little except occupy parts of Prussia. She tried to keep corruption out of government as well, and secularized the lands of many monasteries toward the end of her reign (though she had earlier taken lands her father had secularized and given them back to the Church).
Elizabeth could be capricious, ignoring state matters for weeks to attend balls and dances while her ministers tried to get her signature. Elizabeth tried to consider every possible consequence when making a decision (and was often accused by others of laziness because of how long she took to decide). She tended to stay up all night, both to have fun as long as possible, and because her own capture of the throne had taken place at night. Though Ivan was in prison, several conspiracies to break him out and make him Tsar again were uncovered and she was a bit paranoid about sleeping. However, she was generally known for her alternation between parties and praying, which lasted throughout her life. By 1760, she was suffering from asthma, epileptic seizures, and possibly diabetes; the combination overwhelmed her on Christmas Day 1761, when she died and was succeeded by her nephew Peter III.
Sources: Gina Kaus' Catherine: The Portrait of an Empress and Donald Raleigh and A.A. Inskenderov's The Emperors and Empresses of Russia: Rediscovering the Romanovs.