Free ASP.NET hosting service is free, (sometimes) advertisement-supported web hosting, and is often limited when compared to paid hosting.
Some companies provide free ASP.NET hosting for some period, so the user could test their services.
You could also receive free ASP.NET hosting for some period if you prepay for the hosting services. By example if you pay for 1 or 2 Years in advance, then you will receive 3 to 6 months of free hosting through price discount.