FTP (File Transfer Protocol) is a basic way of using the Internet to move your file transfer workloads. SFTP (Secure File Transfer Protocol) is an alternative to FTP that also enables you to move your file transfer workloads but it adds a layer of security to the process. SFTP uses SSH (Secure Shell) encryption to secure the data and not exposed to outside entities on the Internet as it is being transferred.
If you are looking for an online course to learn AWS, I recommend this AWS Training course by Intellipaat.
You can watch this video on AWS SFTP to understand more: