In ASP.NET Core NULL refers to a lack of value for a reference type or nullable value type. When a variable is assigned NULL it means that it does not currently reference any object. This can be particularly relevant when working with databases as NULL represents the absence of a known value in a column. For example consider a scenario where you have a model class representing a Product entity: public class Product { public int ProductId { get; set; } public string Name { get; set; } public decimal? Price { get; set; } } In this case the Price property is declared as a nullable decimal (decimal?) which means it can hold a numeric value or be NULL. This allows for scenarios where the price of a product may not be known or has not been specified. When reading data from a database if the Price column contains NULL it will be mapped to a nullable decimal in your ASP.NET Core application. To handle NULL values in ASP.NET Core you can use constructs such as the null-conditional operator (?.) and the null-coalescing operator (??) to safely access and provide default values for nullable types. For example: decimal? totalPrice = product.Price ?? 0.00m; This code checks if the Price property of the product object is NULL. If it is NULL it assigns a default value of 0.00m to totalPrice. If it is not NULL the actual value of product.Price is used. Understanding how NULL is handled in ASP.NET Core is crucial for robust data processing and ensuring the reliability of your applications.