Short answers, pulled from the story.
A record in computer science is a composite data structure made up of a collection of fields, which can differ in type but are typically fixed in number and sequence. It is also called a structure, struct, or user-defined type.
A date can be stored as a record with a numeric year field, a month field represented as a string, and a numeric day-of-month field. A circle record can hold a numeric radius alongside a center point record with x and y coordinates.
A record's fields are set by its definition and may be heterogeneous, holding different types, while an array is a collection of elements that all share the same type.
COBOL was the first widely used programming language to support record types, with sophisticated record definition facilities that included nested records and automatic field formatting.
Java introduced records in Java 17, and C# introduced its own version of records as well, both aiming to simplify data aggregate classes with less boilerplate code.
A primary key is unique throughout all stored records, with no duplicates allowed, such as an employee number in an employee file. A secondary key, or alternate key, such as a department code, is not necessarily unique but can still be indexed to speed up lookups.