In recent years everyone has become more security conscious and to protect data when being transmitted the adoption of FTPS is now the default by many hosts, in many cases this is just a simple change in your software if it's supported, any modern software should support FTPS.
FTP (File Transfer Protocol) is a very common way for users to upload and download files to and from multiple locations in most cases this would be your web hosting server. In recent years the preference for FTPS has become the default with less support for plain FTP. As the original FTP protocol had no way to encrypt the data being transmitted meaning your username, password and data is being sent unencrypted anyone could intercept and read the data being transmitted.
FTPS (File Transfer Protocol SSL) addresses the security issues when only using FTP note the S on the end of FTPS as this is not to be confused with SFTP (SSH File Transfer Protocol) which is very different, FTPS in its nature uses SSL/TLS to secure the standard FTP connection so your connection is secured between the sender and the recipien securing the data being transmitted.
FTPS supports 2 encryptions types Explicit (FTPES) and Implicit (FTPS), in most cases you will be using FTPES as this uses the same ports as plain FTP (port 21) so require less changes on the server and client side where as FTPS (implicit) uses port 990 so can require manual changes in your configuration and software.