We use the following terminology.
Within a Relationship, the table containing the Primary Key on the "one" side. For example, Purchaseorder is a parent to Lineitem.
Within a Relationship, the table containing the Foreign Key on the "many" side. For example, Purchaseorder is a child to Customer. PUT/POST JSON provides mechanisms to associate a child with its parents.
A one-to-many relationship between 2 tables in a relational database. Relationships are discovered by Foreign Keys defined in your database. The Sample Database has examples of multiple different kinds of relationships.
Many-to-many relationships are supported in the relational model by introducing Junction tables: a table with Foreign Keys to both end-points. For example, in the Sample Database, Orders can have many Products, and a Product can be ordered on many Orders. We introduce the Junction Lineitem which as Foreign Keys to both, as well as additional attributes (such as QuantityOrdered).
Another name for a Junction Table.
The name by which the Child refers to the Parent, as described here.
The name by which the Parent refers to the Children, as described here.