In the context of sub-playbooks, the three loop types are typically 'For-each', 'Loop automation', and 'Built-in'. The 'For-each' loop is commonly used to iterate over a list of items. 'Loop automation' refers to automations executed in a loop to process data or perform tasks repeatedly. The 'Built-in' loops are predefined loops provided within the system for standard processes. 'Conditional' and 'Data collection' are not loop types; they represent specific tasks within a playbook.