There are a couple of different types of systems.
One is a tank with a drain field. The drain field is usually several perforated pipes that let the septic leech into the soil.
The second is an active system. They usually have a motor or bubbler to keep the tank aerated. Ours is this type and there is no leech field. We pay a yearly fee to have it maintained.
The bad with the leech field is it can plug up. The bad with an aerated tank is it uses electricity and the motor will need replaced on occasion.
Good point, as when I hear to think septic, I think of the type I have had Many times, but there other types.
Mount systems, used in areas with high ground water, the drain field is a mount, built up with sand, the tank is lower, and there is a lift pump to take the water from the tank to drain field. There is a pump and they use a small amount of power. They are pretty tried and true, but not matter how good a pump is, its less reliable than gravity.
There are also lagoons, spray fields, and aeriated systems. Aerator systems are more money, and I haven't been around them at all, but they are used is certain situations. Lagoons are almost unheard of around here anymore, although you may find one left over from decades ago. Spray systems, never ran into on a residential; but its basically a septic tank, and no drain field, instead the effluent is sprayed over a spray field, grasses clean the nutrients from the water, and it evaporates, perks, or flows off as clean(cleanish) water.