Accessing Files and Directories

Absolute and relative paths

Files and directories can be accessed using pathnames.

Absolute pathname: An absolute pathname begins with the root directory and follows the tree, branch by branch, until it reaches the desired directory or file. Absolute paths always start with /.
Relative pathname: A relative pathname starts from the present working directory. Relative paths never start with /.

ls can be used to show directories and files (many different options, ls -a shows hidden files as well)
Another option is tree

pwd shows current directory
cd is change directory (cd ~ goes to home, cd .. goes to parent directory, cd - goes to previous dir)
Another option that saves history of the visited directories is using pushd, this pushes the directory into a LIFO stack, which can return elements using popd.

The ln utility is used to create hard links and (with the -s option) soft links, also known as symbolic links or symlinks( with the -s flag). These two kinds of links are very useful in UNIX-based operating systems.
A link connects two files. In a hardlink, a “clone” is made in the sense that if the original is deleted, the copy still exists and has the content. Also modifying one, modifies the other. In soft links, is just a pointer.
Adding the -i (and the -l) flag in ls allows to inspect the unique number for each file in the filesystem (inode number)
Unlike hard links, soft links can point to objects even on different filesystems, partitions, and/or disks and other media, which may or may not be currently available or even exist.