SSL is one of several encrypted data transfer protocols which are used for the secure communication between computer systems. If a URL entry in the browser begins with https:\\, you are using the SSL protocol.
URL describes a standard, which formally describes how to reach specific services and content on other computer systems by entering a link (such as: https://www.zedas.com). A link is commonly understood as the text which is entered into the entry field of a browser to call up a particular service (e.g. a website).
A VPN is an encrypted data channel which is encrypted privately from each communication partner and is covered via a public network (e.g. the internet). The encrypted private data packets are packed into “public” internet data packets at the source, transported via the public network and unpacked again and unencrypted with the recipient. The popular concept “VPN tunnel” is a synonym for when the content of the private data packets in the public network cannot be seen and move just like in a tunnel across the internet. Metaphorically speaking, a VPN is an extension of your own private network over a public network up to the VPN tunnel end point. If the network, e.g. of an external service provider, is located there, then both networks are connected directly with each other. Restricting access of this external service provider on the private network at the VPN tunnel starting point requires further IT security measures!
sFTP is an encrypted data protocol for the secure transfer of files between an sFTP server and an sFTP-Client.
RDP is a data protocol for the transfer of monitor changes, keystrokes and mouse movements of a remote computer, in principle, this is a tool for controlling a remote computer. While the application programmes on the remote computer are carried out, this computer is operated via a network (e.g. the internet) on another computer.
NAC (Network Access Control) describes various methods of controlling access to a network. End devices (e.g. notebooks) are checked for their conformity with the network access control policy. With NAC, third-party devices are prevented from accessing the network and end devices with network access can be checked for compliance with the security guidelines.