Why are MD5/SHA256 fields not getting displayed in Eloqua forms?

Please explain the exact purpose of the below fields and what is the reason behind those fields which is not getting displayed in Eloqua forms:

MD5 Hashed Business Phone
MD5 Hashed Email Address
MD5 Hashed Mobile Phone
SHA256 Hashed Business Phone
SHA256 Hashed Email Address
SHA256 Hashed Mobile Phone