A shell is a program that interprets what you type and takes the appropriate actions, such as starting up the specified program. Since a shell is traditionally the most common way of interacting with a unix machine, several different shells have been developed and all are greatly customizable. With Linux system, you can also use X-window environment for many of your jobs.
Most users use either tcsh, bash or ksh. The system default is tcsh.
There might be some tcsh settings from old server (Solaris) that get syntax error in new server (Linux). Please let me know if you encounter such problem.