Companies conditions vary. In your search results you will be able to see what kind of licence each company requires. Usually you can rent a scooter with a B (car) or AM/A1 driver's licence.
For motorcycle you will need an A (moto) driver's licence.
To rent a quad bike (ATV) you will need just a car driver's licence.
No licence is required for bicycles. Some rental companies ask for an international drivers permit (IDP), so always check each provider’s conditions.