Germination is the instant at which the seed decides to grow. The seed will be in its dormant state indefinitely until some internal chemical "switch" is switched on. You cant switch growth off again without killing the plant.
Problem is that we don't normally know if the seed has germinated, or is a dead one, until we see something poking above the soil. That's one reason to chit seeds, so you can see instantly the first microscopic root appearing. and you wont waste days or weeks waiting for a shoot to show above the soil, only to find there is no chance.
Many seeds never germinate. Others seeds take their own time. I have had tomato seeds germinate (same batch, same plant pot) from one week to 6 weeks). You could always gently dig up a non-sprouted seed to see what is going on. It it has turned smelly, moldy, squidgy or totally disappeared then there is no hope. Otherwise it is just patience.
What you are asking about to looking after "seedlings". (Q:- when does a "seedling" turn into a plant??)
Most seedlings like it slightly cooler and less damp air than they wanted in order to germinate, and they want sunlight the moment they break through the soil. The food in the seed will only last so long, then they must start photosynthesizing
Less damp air generally means more ventilation, by opening the vents or removing the lid. But that can create draughts or changing temperatures which are not good.
Science only takes you so far. The other 99% is experience, trial and error, or luck.