Profiles

Profiles are customized structure definitions of the resource which describe following in detail:

What element(attributes) of the profiles are used to create a sample data structure.
What is the cardinality of the element, which explains if the element is mandatory or optional, can the elements be repeated multiple times and data type of each element.
If the element has any fixed values, binding to any ValueSet(list of possible values to be used)
Extensions to hold information that does not fit in the profiles defined by FHIR structure.