Parametric (modeling) : the ability to drive the geometry by parameters. CATIA can manage many kind of parameters, from 'length', 'area' to 'Real' or 'string' even 'point' 'curve' or 'surface' parameter. You can define parameters value with relation ==> A = B + C or if you have KWA (knowledgeware) license, you can create rules 'if A > C then C = D else C = E'. You can also drive parameters with an excel file using 'desisgn table'....
Geometrical links : the ability to control the geometry by a relationship between geometrical elements: 10 points define a curve that define a surface, if you modify the points, it will modify the curve and the surface. The link between geometrical elements can be within the same file or from different file. The skeleton methodology like most CATIA geometric construction is base the the relation between geometrical elements.
Note: Parametric and geometrical links are going one way: A define B you can not have a circular reference A define B define C define D define A.
You said you are learning V5, did you ask this question to your instructor?
Eric N. indocti discant et ament meminisse periti
