To help you understand takkanot, take a look at these excerpts:
“One must sparingly use takkanah as one must sparingly use the constitutional amendment process in United States law. There is a danger of abuse. There is a danger of social whim becoming standardized through legislation, making enforcement and repeal difficult…One must decide whether the particular social trend is worthy of being translated into law…one ought to be convinced that the social situation occasioning the takkanah will be of some considerable duration,” pg. 41 of “In Partnership With God” by Byron Sherwin.
“One other important aspect of this period [of the Acharonim, those who wrote after the Shulchan Aruch] is the synods or councils that took place and the takkanot (revisions; literally, ‘fixings’ of the law) that they produced….These synods probably based their authority on the acceptance of their respective communities. The members of the communities took a vow that they and their descendants would accept the synod’s decisions. In that way, Jewish law was changed considerably,” pg. 67 of “Conservative Judaish: Our Ancestors to Our Descendants” by Elliot Dorff
“The takkanot may represent a change in the content of the law, as their name implies, but they nevertheless are part of Jewish law because they were enacted by its duly authorized representatives,” pg. 87, ibid.
“During the Talmudic and medieval ages authorities enacted many new ordinances that were not found previously in the Bible and yet were legally binding on the Jewish community.
Examples of takkanot enacted in the days of the Mishnah are: (1) a man must support his children while they are minors; (2) a gift of more than one-fifth of one’s property for charity is forbidden….
The rabbis never enacted takkanot arbitrarily. Every enactment was seriously regarded, since it represented change, and occasionally a break with older practices. But they recognized the growing needs of the Jewish community in a more complex society…Every takkanah was to be an improvement over the existing practice and yet could not move away from the intent or spirit of the biblical law,” pg. 405 of “The Language of Judaism” by Simon Glustrom