what does using mean c# code example

Example 1: using in c#

//doing with using function
using (var font1 = new Font("Arial", 10.0f)) 
{
    byte charset = font1.GdiCharSet;
}

//or
using var font1 = new Font("Arial", 10.0f);
byte charset = font1.GdiCharSet;

Example 2: using statement c#

using (var reader = new StringReader(manyLines))
{
    string? item;
    do {
        item = reader.ReadLine();
        Console.WriteLine(item);
    } while(item != null);
}