This is what we found on Wikipedia regarding the Palace:

A palace is a large residence, often serving as a royal residence or the home for a head of state or another high-ranking dignitary, such as a bishop or archbishop. The word is derived from the Latin name palātium, for Palatine Hill in Rome which housed the Imperial residences.

Most European languages have a version of the term (palats, palais, palazzo, palacio, etc.) and many use it to describe a broader range of buildings than English. In many parts of Europe, the equivalent term is also applied to large private houses in cities, especially of the aristocracy. Many historic palaces such as parliaments, museums, hotels, or office buildings are now put to other uses. The word is also sometimes used to describe an elaborate building used for public entertainment or exhibitions such as a movie palace.

A palace is typically distinguished from a castle in that the latter is fortified or has the style of a fortification, whereas a palace does not.