Eggs are eggs, fry are baby fish, spawning is laying eggs, courtship is what happens before egg laying, some fish build nests some don't, species vary as to care of nest/young. egg sack fry are tiny wrigglers that feed mainly off the yolk reserves they carry after hatching and tend to be very vulnerable to damage and disease. Aros are often sold at this stage and while they are cheaper then I would not buy one but maybe I'm just chicken.
To confuse you there are also smolts, parr, planktonic fry, neotonous young, elvers, and yellows.