On a literal level, the word "reform" means to "reshape" or change. It usually carries a sense of improvement, often of something that is corrupt or functioning badly. Thus one might say "We need to reform voting procedures in country X due to evidence of widespread corruption." It is used in the context of human beings or political structures, but not of inanimate objects. One can speak of a "reformed drug addict" who has been rehabilitated but not a "reformed car" after an oil change and tune up.
In English literary studies, there are two specially significant uses of the term "reform". One use refers to the Reformation, or birth of Protestantism, in 1517. This was a movement within Christianity to "reform" what were considered the abuses of the Roman Catholic Church. The term "reformed" church means a Protestant one.
Next, in Victorian literature, the term "Reform", often capitalized, refers to the Reform bills in English Parliament, especially the Reform Bill of 1832, that widened the voting franchise. When characters in Victorian novels discuss reform, they mean a set of political changes that give more political power to the middle and later working classes and make government more representative.