Member Rara Avis
There are a number of different ways to record. Obviously, you can use it like a VCR, setting date and time manually. It also has a built-in program guide, and if you see an upcoming program of interest you can immediately set it to record straight from the on-screen guide. Another option is to issue a Season Pass. Those allow you to specify a show and let the system figure out dates, times, and even channels. It can, for example, find every episode of Star Trek: TNG on any available channel for the next two weeks, simply by searching its internal program guide. Periodically, it contact home base (phone, satellite or cable) and downloads an updated program guide.
Want even more flexibility? You can also establish a WishList based on Title, Director, Category, Keyword, or Actor. Tell the system you like Jennifer Aniston and it'll find all episodes of Friends, any movies playing with her listed, and will even record Jay Leno if she happens to be a guest.
Finally, TiVo will even offer its own Suggestions, based on what you've recorded in the past, and those too can be set to auto-record (not a great idea, as it makes a LOT of suggestions).
Additionally (and just for Karen!), if you just happen to flip to a channel, any channel at all, the box will automatically start recording, storing up to an hour of "live" television on its disk. That means, on any show at any time, you can push the pause button and take a break. When you return, you'll be watching the recording instead of the live show. Pause long enough (usually ten minutes on most network shows) and you'll be able to fast-forward through all the commercials, ending your recorded version of the show just about the same time the live one is finishing. It's dang near magic.
The TiVo box is basically a computer, running the Linux operating system, with proprietary programs providing control of pretty much anything you would want. The bigger the hard disk, the more hours you can record. The base system handles approximately 35 hours. The "key" to the system is that internal program guide, since the software can search it just like a database. There are similar systems surfacing, and you can even turn your PC into a DVR (Digital Video Recorder), but TiVo was the first and arguably still the best.