RAID
Redundant Array of Independent (or Inexpensive) Disks. Type of disk, often used on servers, where several physical disks are combined into an array for better speed and fault tolerance.

Level 0 implements data striping where file blocks are written to separate drives. Does not provide fault tolerance, because failure of one drive will result in data loss.
Level 1 implements data mirroring. Data is duplicated on two drives either through software or hardware. Provides faster read performance than a single drive.
Level 2 - not used in practice. Data is split at bit level at written to multiple drives.
Level 3 - requires at least 3 drives. Data block is striped at byte level across drives and error correction codes (parity info) is recorder on another drive. Provides fault tolerance but slower writing performance.
Level 4 - Similar to Level 3 but provides faster performance because it uses blocks for striping.
Level 5 - Similar to Level 4 but improves performance but also striping parity info across multiple drives.
Level 6 - Similar to Level 5 but also uses second parity scheme for better fault tolerance.
Level 7 - Proprietary RAID design by Storage Computer Corporation. Faster than other levels because it uses multiple levels of cache and asynchronous I/O transfers.
In addition multiple RAID levels can be combined to improve performance or reliability.

RAM
Refers to the Random Access Memory of the computer. Measured in MB or GB. The more the RAM, the easier a server can perform its tasks.

Raw Logs
Raw access data updated in real-time that can be downloaded and used by any statistics program. Typically each line show the user's IP, date and time of the access, what kind of request was done, which document was requested, HTTP status code, bytes transferred, referrer, and user agent info.

If a host doesn't have statistics, you'll need access to raw logs to identify who your site's visitors are. Analyzing raw logs can also provide more detailed look at site accesses than stats.

Real Audio / Real Video
Real Audio/Real Video enables users of personal computers and other consumer electronic devices to send and receive audio, video and other multimedia services using the Web.

Redundant Backbone Connection
Multiple connections to Internet backbones, or main network connections composing the Internet.

Referrers
As the name suggest, referrers means the sites which "refer" traffic to your web site. It is usually recorded in the log files and analyzed by the web stats.

Register (Domain Name)
Since every domain is unique, registries have been set up to assign domains to individuals and organziations. When a domain is registered with the appropriate registry, that domain is assigned and becomes no longer available for anyone else to use.

Typically, there are registration and renewal fees (local registry fees) associated with the right to use a domain. However, there are some TLDs that are provided at no charge.

Registrant (Domain Name)
The entity, organization or individual that will be using the domain name.

Registrar (Domain Name)
Some registries don't provide the ability for end users to register domains with them directly. They might require end users to purchase the domain through an internet provider that is acting as the registrar.

Registry (Domain Name)
An organization responsible for assigning domain names for the TLD that they manage. Furthermore, it is their responsibility to update the global DNS tables that all nameservers use to resolve domain names. For example, InterNIC is the registry for .COM, .NET and .ORG domain names.

Renewal (Domain Name)
Most TLDs need to be renewed at some scheduled yearly interval. This is an opportunity for both the registrant and the registry to update their records as well as collect any applicable renewal fees.

Reseller Plans
Many hosting providers allow you to be a reseller of hosting space earning a commission off of each sale. If you intend to be a provider of hosting services, you should investigate this option as you decide where to host your web site.

Many hosting companies offer discounts (in addition to revenue opportunities) to companies that wish to remarket their web hosting services.

Resolve
The term used to describe the process by which domain names are matched with corresponding Internet Protocol (IP) numbers. "Resolution" is accomplished by a combination of computers and software, which use the data in the Domain Name System to determine which IP numbers correspond to a particular domain name. Basically, it is translating a number to the name you see in your browser for the web site you are visiting.

RJ-11
A standard connector that is used to connect to the telephone line.

RJ-45
A standard connector that is used to connect to the Ethernet network.

Root Server
A machine that has the software and data needed to locate name servers that contain authoritative data for the top-level domains.

Router
A device which connect 2 or more computer networks together and direct traffic between them.

RFC
Request For Comments. The name of the result and the process for creating a standard on the Internet . New standards are proposed and published on line, as a Request For Comments. The Internet Engineering Task Force is a consensus-building body that facilitates discussion, and eventually a new standard is established, but the reference number/name for the standard retains the acronym RFC, e.g. the official standard for e-mail is RFC 822.

RSA
A public key cryptosystem developed by Ron Rivest, Adi Shamir, and Leonard Adleman. It can be used to encrypt session keys and to generate digital certificates.