Is Skyrim a DVD-ROM or a PC-ROM for PC?

You mean a CD-ROM, not a PC-ROM. It's most certainly going to be a DVD-ROM because games have gotten far too large for a CD. CDs only hold on average about... 700MB give or take, and we've had games that were too large for one CD for years before DVDs came out. DVDs hold about 4.3 GB (roughly 7.9GB or so for dual layer DVDs), and to put that into perspective, 1GB is 1024MB, so a single DVD can hold at least 5-6 times more data than a CD. If Skyrim was on CD, it'd have to come on at least 6 CDs which would be ridiculous in 2011 when DVDs are so commonplace. The thing is that most games these days are getting too big for DVDs as well. Call of Duty: Modern Warfare 2 came on two DVDs for PC. Final Fanfasy XIII for the Xbox 360 comes on 3 DVDs compared to the PS3's single Blu-ray disc (Blu-rays hold about 25GB and up to 50GB at least for dual-layer discs).

Usually Games would be DVD-ROM, since they would be larger than 1 GB. PC-ROM, I think which is CD-ROM, is significantly smaller and holds only up to 500 MB. They're great for songs and music CD's but not for PC games.