Data processing is any use of personal data other than for personal reasons, like gathering and storing staff or customer personal data for use in your organisation.
Personal data is any data about individuals who can personally be identified from that data. Examples include names, addresses and birthdates.
There is also a further 'special category' of 'sensitive personal data', which is awarded greater protection. Examples include information about sexual life, genetics, and physical or mental health.
Criminal offence data (ie personal data relating to criminal convictions, criminal offences, and related security measures) is treated separately from personal data and special category personal data. It is also subject to stringent controls.