The value implicit parameter

The implicit parameter value is used in the set accessor in property and indexer declarations. It's an input parameter of a method. The word value references the value that client code is attempting to assign to the property or indexer. In the following example, TimePeriod2 has a property called Name that uses the value parameter to assign a new string to the backing field name. From the point of view of client code, the operation is written as a simple assignment.

class TimePeriod2
{
    private double _seconds;

    public double Seconds
    {
        get => _seconds;
        set => _seconds = value;
    }
}

For more information, see the Properties and Indexers articles.

C# language specification

For more information, see the C# Language Specification. The language specification is the definitive source for C# syntax and usage.