Neophyte characters are those that have not chosen a development path.
After your first adventure, assuming you are alive and have accumulated enough experience, you can advance into any character class of your choice that you qualify for: HP increase as appropriate, though you have a minimum of 4. You gain all the normal proficiencies, abilities, etc., for your new class. In the case of duplication, you gain no benefit. You do not gain any additional equipment automatically (unless game circumstances allow it), except that Wizards gain a spellbook for free, and clerics/druids gain a holy symbol, if they do not have one already. If you had spell casting ability as a Zero Level character and choose not to go into that type of class, the brief empowerment to cast the cantrips learned vanishes as the mental and/or spiritual processes built up are neglected and wither.
Neophyte characters should have a some degree of Fortune, Wonderment, or Inspiration if they are to be put into a situation similar to 1st level characters and expected to survive.