Glasnost was the policy of openness, allowing greater individual and political freedoms within the USSR to open up society and thus allow the reform an d restructuring of the economy.
Between 1988 and 1989 new political organisations such as the opposition party, the Democratic Union being tolerated, and the publishing of books by dissidents and of those critical of the regime. Religion was also officially tolerated for the first time since the fall of Tsarist Russia with churches, synagogues and mosques in the southern Muslim republics reopening.
Glasnost also ended censorship of the press within the USSR. In May 1989 the Congress of Peoples Deputies was elected, the first contested national elections held by the Communist Party, and this was a body largely representative of public opinion, and the body had complete freedom to debate and criticise the government, a far step from previous regimes.
Finally, Glasnost led to cancelation of Article 6 of the Soviet Constitution, an article that guaranteed the Communist Party the leading role in the USSR. This meant all Party officials would have to be elected by 50% of the electorate, and in March most long term officials in the Congress of Deputies were thrown out, AND Gorbachev was elected as the first executive president of the USSR.
This policy ultimately led to the collapse of the USSR as the Communist Party was unable to maintain control over all the disparate Republics within the USSR, and this led to the independence of these states such as the Baltic States and central Asian republics, and the breakup of the USSR.
Perestroika was the efforts to reform and restructure the out-dated Soviet economy in order to avoid economic crash and crisis. Due to hardliners, and much of the old soviet leadership’s lack of willingness to reform and change, this need for economic reform necessitated political and social reform in the form of glasnost, in order to encourage more innovation in industry etc.
In his effort to reform the economy and bring the USSR onto economic parity with the Western World, Gorbachev broke with doctrine by allowing and encouraging limited private enterprise (making it legal for the first time since 1928 in May 1988), as a means to encourage innovation and productivity (the belief being that with total state control employees felt there was no opportunities for betterment and were thusly unmotivated and unproductive) and decreased the Communist Party’s interference with the economy and industry as a whole.
Feeding into this was Gorbachev’s efforts to end the arms race, as it was clear the USSR could not afford to keep up with the USA’s developments such as the Strategic Defence Initiative.