I am not sure what Massage is but I assume you are talking about masking data.
Usually you mask data related to the HRMS like Employee Salaries, Bonus or any critical goverment related data or customers etc.
Please refer this If you are looking for Masking.
Hope this helps!
You mask anything your organization deems too sensitive to be available in a development environment. There is a trade off between masking data and crippling your developers, so I would suggest being careful. Though with GDPR etc, any personal information should be removed unless you have an appropriate framework in place to protect your dev instance (most orgs set passwords to something short and memorable - this isn't protecting your data!).