FTP sever name and it is IP address

Hi,

I am given an FTP server name and IP address, such as:

1. st.avadfaoifdaslkf.com OR 25.136.27.2

I am just wondering:

1. How would PI know "st.avadfaoifdaslkf.com" is associated to "25.136.27.2"

2.If I am using SFTP, how should I get the "Server fingerprint"? Should the FTP server admin provide me that information?

Big thanks in advance

Blue