Real Brisker, Halocha is a set of practical obligations, which apply to every Jew. They are based on the Laws of the Torah.
Sometimes, there is a machlokes of Rishonim or Achronim about a certain obligation. At times the Halocha follows the lenient opinion. It is a ma’alah to conform to the stringent opinion, and it’s called a chumra. Chumros are not obligatory, unless accepted as a neder. A different example of a chumra is when a person does something extra, not required by Halocha, to distance oneself from aveira.