An "endorsement" to a policy is a change to the coverages in that policy made within the time period that coverage is in effect. This can get fairly complicated, especially with "out of sequence" endorsements: overlapping endorsements, retroactive to some date prior to the date the endorsement is made, etc.

The process of making an endorsement can be a simple change or a complex interviewing and rating process as with PolicyQuoting.

The result is a policy more complicated than the original because the coverage periods of the policy may overlap with each other.

Side note: the more complicated endorsements are not always explicitly handled by "legacy" policy systems, rating engines, etc. In some complicated endorsements the carrier just starts over, writing a new policy.