Please provide historical understanding of the selected primary source. What does Lenin believe and hope to gain? https://www.marxists.org/archive/lenin/works/1901/witbd/i.htm

The main thesis of Marx's political treatise was to advocate for revolutionary socialism as the only means of annihilating capitalism. He hoped to gain a complete reform of the entire political apparatus in Russia through violent means.
To that end, Lenin questioned the propensity of fellow socialists to point out the supposed failures of dogmatic Marxism. Unquestionably, Lenin's "dogmatic Marxism" favored radicalism rather than evolutionary (moderate) reformation.
Lenin began his treatise by drawing attention to the schism within international Social-Democracy. He pointed to alarming disputes between moderates and radicals. He provided examples of the rising conflict between "Lassalleans and Eisenachers, between Guesdists and Possibilists, between Fabians and Social-Democrats, and between Narodnaya Volya adherents and Social-Democrats." Lenin saw the schism as a crisis of grand proportions.
The Lassalleans and Eisenachers were nineteenth-century German working-class political parties. As a petty bourgeois-socialist, Lassalle advocated against revolution as a means of socialist opportunism. Marx and Engels resented Lassalle's nationalistic focus and what they derisively termed "utopian dogmatism." Meanwhile, the Eisenachers were members of the German Worker's Party; they favored revolutionary struggle and unequivocally rejected nationalism and Bismarckian capitalism.
In France, there were the Guesdists and Possibilists, representing two divergent strains of French socialism. The Guesdists advocated a proletariat-led revolutionary overthrow of the capitalist bourgeoisie system (much like the German Eisenachers), while the Possibilists maintained that capitalism only needed to be reformed.
In England, the Fabians advocated for moderate, gradualist reform rather than revolutionary struggle; their position was in complete opposition to that held by the Social Democrats.
For his part, Lenin hoped that the conflict between the revolutionary and moderate wings of the worldwide socialist movement would result in the ascendancy of the former. He greatly lamented the "decisive turn from revolutionary Social-Democracy to bourgeois social-reformism." Lenin believed gradualist reform to be a travesty and a betrayal of Marxist goals. In his treatise, he directed his bitterest criticism toward Eduard Bernstein and his strain of reformist, evolutionary socialism.
Lenin maintained that "Bernsteinism" would result in the "humiliation and self-degradation of socialism in the face of the whole world" and the subsequent "corruption of the socialist consciousness of the working masses." Lenin argued that the "new 'critical' trend in socialism" gave cover to a destructive form of socialist opportunism. Lenin wanted concrete, revolutionary action, not pacifist reform. This is the main theme of Lenin's treatise.
Later in the treatise, Lenin vigorously defended the necessity of “ruthless criticism of the Bernsteinian and other anti-revolutionary tendencies" within the world socialist movement. Lenin argued that revolutionary thought should be homogenenous and intolerant of ecleticism. Notably, Lenin's radical views led to the split between his Bolsheviks and the more moderate Mensheviks within the Russian Social-Democratic Labour Party (RSDLP). To read more about this, please refer to The Difference Between The Bolsheviks and Mensheviks.
Lenin maintained that unadulterated revolutionary theory would be crucial to the success of the international socialist movement and that "vanguard" revolutionary fighters should accept no other guiding philosophy in their struggle against capitalism.
http://www.differencebetween.net/miscellaneous/politics/difference-between-bolsheviks-and-mensheviks/

http://www.themontrealreview.com/2009/On-Lenin-What-Is-To-Be-Done.php

https://www.marxists.org/archive/lenin/works/1901/witbd/i.htm