A contract where the employee is not guaranteed any hours and is only paid for hours worked.
These are largely banned in Ireland (with minor exceptions). You must give employees "Banded Hours" contracts that reflect their actual working reality over a 12-month reference period.
You can have a "Casual" contract where there is no mutuality of obligation (you don't have to offer work, they don't have to accept). However, if this person falls into a regular pattern (e.g., every Friday night for 6 months), they may accrue rights to a banded hours contract. True casual employment must be irregular and intermittent.
Effectively, yes. Following the Employment (Miscellaneous Provisions) Act 2018, zero-hour contracts are prohibited in most circumstances. You cannot keep an employee on a contract that guarantees zero hours unless the work is genuinely casual/emergency in nature (e.g., substitute cover). You must generally offer "Banded Hours" contracts that reflect the reality of the hours they work.