First Normal Form (1NF) is a property of a relational database table that ensures each column contains atomic, indivisible values. This means that each entry in a column must hold a single value, not a list or set of values. Additionally, each row in the table must be unique, which is typically achieved by using a primary key. To achieve 1NF, a table should not have repeating groups or arrays. For example, if a table contains a column for phone numbers, it should not list multiple numbers in a single cell. Instead, each phone number should be in its own row, ensuring clarity and consistency in the data structure.