Ok. basics it is…
A terminal (And x-term included) is realy just a window or a view into a text based command line environment. that environment runs something called a shell, that contains rules and commands for how you can interact with the OS using text.
SSH is an abreviation for Secure SHell. It is a protocol and a method to connect remotely to a linux host using encryption. Telnet is another way to connect remotely, but is not encrypted. The big difference is that telnet sends everything in clear text, so anybody sniffing your remote session will see what you write, and be able to snap up your username and password. SSH encrypts everything, so that your session stays private.
typeing SSH into a terminal window (using your local shell) do not open a new graphical window. It opens a new shell connection to the remote host, in the same terminal window you are currently using.
SSH and terminal windows are used to run commands and do tasks running those commands.
FTP (File Transfer Protocol) is a protocl for transfering files between different hosts. FTP in it self have no graphical interface, it merely defines protocols for to host to be able to transfer files. It is your FTP client that has the graphical user interface. SFTP (Secure File Transfer Protocol) is the same, but encrypted.
The root user is limited to local shell use by default. It may be opened for remote use, but not recommended (At All). Use your MC user. NEVER use root, unless you are updating your system (or MineOS).
If you are running from a windows PC remotely I reccomend putty (http://www.putty.org/) for ssh connections and filezilla (https://filezilla-project.org/) for sftp transfers.
It also sounds like you need to read up on linux: https://www.linux.com/learn/complete-beginners-guide-linux%20
This is highly recommended, since MineOS runs on top of a linux version, and you will need to know how to use linux to sucessfully use MineOS (over time).
Using laptops for MineOS and Minecraft is not always simple. In particular if you wish to use it on your wireless network. The older ones are often not quite fast or strong enough to run minecraft servers lag free. Especially if you are planning on running more than one minecraft server, or one of the heftier ones like the FTB-class of minecrafts servers.