Normalization theory is constructed around the concept of normal forms that define a system of constraints. If a relation meets the constraints of a particular normal form, we say that relation is in normal form.
By definition, a relational database is always normalized to first normal form, because the column values are always atomic. That is, a column can contain one and only one value or null.
But to simply leave it at that invites a number of problems including redundancy and potential update anomalies. The higher normal forms were developed to correct those problems.