Unix and Linux is operating-systems -- like Windows or OS X -- not a language per se. It's a platform for running applications (programs) on (like web-browsers, spreadsheets, databases). Of course there are some tools for handling the system (like moving around files), but first and foremost you run other programs (applications) on top of an operating system. Of course the programs must be made for the particular OS, you can't run a Windows program under Unix/Linux or vice-versa (at least not directly).
The different shells (bash, zsh, tcsh, pdksh, ...) -- the command interpreters -- comes with a built-in "programming language" to make so-called "shell scripts" (simple programs to do routine tasks or repeat an operation on multiple files/directories).
Apart from the shells, Unix/Linux comes with lots of commands and utilities for doing various things on your system:
Copying (cp), renaming/moving (mv) and deleting (rm) files
Creating (mkdir) and removing (rmdir) directories, and changing into them (cd)
Listing files in a directory (ls)
Listing processes (running programs) on the computer (ps, top)
Killing processes (kill)
Adding and deleting users and groups
Editing files (nano)
Installing/uninstalling programs
Finding files in directory-tree (find)
Find a string in a file (grep, egrep, fgrep)
Disk usage (df, du)
Compressing files (gzip, bzip2, compress)
Making archives (tar, cpio, ar, zip)
There are a number of commands -- filters -- that may do interesting things on text-files:
Number lines (nl)
Sort (sort)
Concatenate multiple files (cat)
Reverse a file (tac)
Replace characters (tr)
Cut-out columns (cut)
Merge two files (paste)
Find differences between two files (diff, comm)
Lines at beginning (head) or end (tail) of files
Write only screen-fulls (more, less)
Break to a certain width (fold)
Remove duplicate lines (uniq)
Split a file in pieces (split)
Count character, words and/or lines (wc)
In addition there are two "universal" filters, working on lines (sed) or columns (awk).
In addition, Unix/Linux usually comes with at least a C-compiler, and probably a C++-compiler and assembler too.
Unix and Linux also comes with servers for various Internet-services, like POP (mail), SMTP (mail), HTTP (web) and FTP (files).
There are also possible to run a graphical user interface -- X -- that looks a bit like Windows.