There are two primary ways to access and utilize linux. For further information on using either of these methods, please see the Old School CLI and New School GUI drop down menu pages.
The old school way is to connect with some form of command line interface connection such as ssh or the older telnet or rlogin protocols and access a command line interpreter known in the Unix and Linux world as a shell.
If you prefer to use a command line interpreter or shell, it is best to use ssh to connect rather than rlogin or telnet because ssh provides an encrypted channel so that your login and password and any other data that transverses the connection can not be captured or sniffed by unauthorized third parties.
If you are originating from a Windows machine, a free program called “putty” can provide this functionality. Putty is also available on some Linux systems. On Mac and Linux systems, an ssh client is a native part of the operating system.
New School GUI
The new school way is to connect with a remote desktop application such as X2Go, NX, VNC, or RDP to provide a full graphical remote desktop complete with graphical applications, keyboard, mouse, monitor, and if you use X2Go even sound, printer, and USB devices.
X2Go is the preferred method of connecting graphically. It is based on remote X-windows but it performs round-trip reduction that eliminates many X-windows back-and forth displays, it has excellent compression that makes even real-time video possible over a reasonably fast connection, and it securely tunnels everything through ssh so your session is secured from third party eavesdropping.
You can find an X2Go client for Windows, Mac, or Linux at the X2Go.org. The X2Go client for Redhat will work with Centos and Scientific Linux. The X2Go client for Ubuntu will also work with other Debian derived Linux systems.