Regarding the Prerequisites of sftp and ftps

Hi Experts ,

               i want know about the scenario file to file where the protocols are ftps and sftp. can u please give me detailed explination about each protocol .

1. when we will go for the ftps

2. when we will go for the sftp

3. what are the prerequisites to do in both the ftps and sftp.

4. what are the advantages of ftps and sftp as well as disadvantages.

Thanks

Giridhar.