Realationship between Customer table and Sales table

Just wanted to know what type of relationship does these table hold, as the customer id is primary key which is unique and the customer id in sales table is the one corresponding to the sales and the column representing customer id has possible scenarios of duplication, which means we are banking on customer table to identify the customer who purchased x product. Going by this logic is is it correct to say that the two table establishes one to many relationship.