What is the relation between Opportunity and opportunityLineItem in Salesforce?

Opportunity:
Opportunity object stores data of potential sales and pending sales.
One opportunity can only have one pricebook.
One opportunity can contain one or many line items.
Product:
Product object is a catalogue of items or services for sales.
A product may contain one or more different sets of prices (PriceBookEntry).
OpportunityLineItem:
List of products that link with opportunity containing data on types of products and respective prices.
One opportunity line item can only be linked to one opportunity.
One opportunity line item can only be linked to one price book entry.