As an author who wrote happily under the Soviet Union and began the literary method called "social realism," in Mother Gorky tells the tale of the proletariat protesting against both the grand Russian Czar as well as capitalism, eventually leading to the October Revolution.
The story focuses on a worker in a factory called Pelagueya who is bent on ignoring the politics of the upheaval in Russia so that she can concentrate on her personal life. Pelagueya becomes a big symbol for the worker who just struggles to live day-to-day.
The story also focuses on Pelagueya's son Pavel who, instead of focusing on personal life, chooses to focus on the political upheaval by joining the revolution. Pavel ends up inspiring others to join the revolution as well, showing their disagreement and disillusion of the capitalism of Russia at that time.
Eventually, Pavel is brought to trial (with his comrades) and confronts the coldness of the judges. Through the trial, Pavel gives a passionate speech supporting socialism after which Pavel (and his friends) are exiled. More socialists are tracked down. Meanwhile, someone prints Pavel's speech. Pelagueya, herself, vows to deliver them to the neighboring town. On her way she is beaten by lawmen as she scatters the leaflets.
The reason why Gorky's story is called Mother is because Gorky considers Russia (and especially Soviet Russia) as the "mother country" who will support all of her citizens and assist them in bolstering their rights.