It might seem to some people that the law loves nothing more than to be confusing to laypersons. In some states, a guardian is needed to take care of an elderly person who can no longer take care of him or herself. In other states, a conservator is needed to do the same thing. Elsewhere both might be needed.
Traditionally, the two words mean different things.
Guardians and conservators had different responsibilities as explained by the Motley Fool in "What Is the Difference Between Conservatorship and Guardianship?"
Traditionally, a guardian is a person designated by a court to take care of a person's physical needs. The guardian makes health care decisions for example. A conservator is a person appointed to take care of financial affairs.
Similarly, when executing a general durable power of attorney and a health care power of attorney, having these distinct guardianship and conservatorship positions allows for different people to be assigned to the different roles.
A good guardian might not necessarily make a good conservator.
Over time the differences between the two positions have become blurred and some jurisdictions have done away with them completely. Others have kept them.
Even in those states that have nominally done away with either a guardianship or a conservatorship courts are generally still able to appoint different people to the different roles if necessary.
If you have questions about the rules in your state, speak with an elder law attorney.
Reference: Motley Fool (March 18, 2016) "What Is the Difference Between Conservatorship and Guardianship?"