The Internet Corporation for Assigned Names and Numbers, the Internet's key oversight agency, is nearing a vote on creating a voluntary ".xxx" domain name for pornography sites.

Questions about the proposal and domain names in general:

Q. What are domain names?

A. Behind every machine connected to the Internet is a series of four numbers known as an Internet Protocol address. Domain names were created as an easy-to-remember shortcut — it's much easier to remember "ap.org" than "165.1.59.220." When you type a domain name into a Web browser or an e-mail message, your computer checks a series of domain name servers to match the name to the equivalent numeric address.

Q. How many domain names are there?

A. There are currently 266 suffixes with a handful of others approved but not yet functional. Most are for specific countries or regions, such as ".fr" for France and even the legacy ".su" for the Soviet Union. Others are reserved for specific uses, such as ".mil" for the U.S. military and ".museum" for museums. Relatively few — the most popular being ".com" — are truly for global and universal use.

Q. How do names get added?

A. Most of the names date to the system's creation in the 1980s. In 1998, the U.S. government, which funded much of the Internet's early development, selected ICANN to oversee Internet addressing policies, including the addition of domain names.

ICANN approved the first major round of additions in 2000, selecting seven names but essentially rejecting ".xxx" and several others. ICANN opened a second round in 2004 and received bids for 10.

ICANN also has approved region-specific codes, including ".eu" for the European Union and ".ps" for the Palestinian territories.

Q. Where does ".xxx" fall?

A. The current proposal grew out of the 2004 round of bids, which ICANN specifically restricted to "sponsored" names, meaning their use would be limited to a specific community, be it the travel industry or porn sites.

ICM Registry Inc., a Florida startup founded by entrepreneurs with backgrounds in domain names and U.K. Internet companies, sought its creation. If approved, its use would be voluntary, just as with any other domain.

Q. Why has a decision taken so long?

A. Of the 10 applications, only ".xxx" and ".post" for postal services remain pending. After considerable debate, ICANN rejected the ".xxx" proposal last May, but ICM came back with a new plan with more specifics. Even before that got a vote, ICM returned with yet another proposal to address concerns about ICANN's enforcement abilities and the independence of a nonprofit body that would set rules governing the domain's use. Each step meant a period for public commenting, and opposition among adult Web sites and religious groups remains strong.

Q. What happens if the name is rejected?

A. That would largely depend on the wording of ICANN's resolution, but ICANN rarely throws out a bid outright, meaning ICM likely could return later with a revision to address any concerns. However, ICANN appears ready to close the 2004 round of bids as it prepares to launch a new round. ICM also could seek to have the decision reviewed through ICANN channels or file a lawsuit if it believes ICANN failed to follow its own guidelines.

Q. What happens if the name is approved?

A. Assuming the U.S. government does not wield the veto power it has over ICANN, ".xxx" would be entered into the domain name system within months. ICM would establish a program to set aside certain names, such as trademarks and geographic places. Web sites wanting any remaining name would sign up with an approved registration company, which would forward to ICM $60 for each name sold. No site would be required to use the domain, and sites would be free to keep their existing names under ".com" and elsewhere. Parents could set their filtering software to block all ".xxx" sites, although that alone won't stop all such sites given its voluntary nature.

Q. Shouldn't ".xxx" be mandatory then?

A. Mandating the domain's use would raise significant problems, namely how to define pornography. Should any site with nudity be classified? What about artistic or educational sites, such as ones on breast feeding? And who should decide, given conflicts between pornography and speech laws around the world?

Even if those issues are resolved, such a requirement wouldn't stop pornography entirely: A child could simply type in the equivalent numeric address to reach a porn site directly.