Guardianship specifically refers to the legal authority an appointed adult has over a child (or an impaired or incapacitated person). While guardianship over a child can be comprehensive, empowering the appointed guardian to make various medical, legal, and other decisions on behalf of a child, it may also be limited in scope, depending on the details of a given case and the needs of a child.
In contrast, a conservatorship grants one adult the authority to make financial decisions on behalf of another impaired or incapacitated person. Conservatorships tend to be more limited in scope and authority than guardianships.