GAP Manual: 16.11. Algebraic Extension Records

Since every algebraic extension is a field, it is represented as a record. This record contains all components, a field record will contain (see Field Records). Additionally, it contains the components isAlgebraicExtension, minpol, primitiveElm and may contain the components isNormalExtension, minpolFactors and galoisType.

isAlgebraicExtension:
is always true. This indicates that F is an algebraic extension.

minpol:
is the defining polynomial of F.

primitiveElm:
contains RootOf(F.minpol).

isNormalExtension:
indicates, whether F is a normal extension field.

minpolFactors:
contains a factorization of F.minpol over F.

galoisType:
contains the Galois type of the normal closure of F. See section GaloisType.