The subscription fee is for the guide data. When the TiVo makes it's daily call, it downloads the new data. This usually results in about two weeks of data on the TiVo at all times.

If you don't pay the subscription fee, the TiVo works like a basic VCR. You have to setup manual recordings for certain times. And none of the recordings will be named.

Having a TiVo without a subscription is like owning a car with no gas in it.