What is an FTP and how does it relate to Dacast?

It stands for File Transfer Protocol, and deals with FTP clients like Filezilla as a way to upload content to your account. FTP clients are external programs which allow you to connect to a web service, like Dacast, using login details that include a:

server
username
password

This is the suggested method for uploading files around or over 1.5 GB in size. If you need help on using this feature over Dacast, please refer to this video tutorial.