In the center is the block.
This is the largest portion of the engine
It has small holes bored through it for water, oil, bolts, etc.
It has large holes bored through it, the cylindars.
The cylindars are where the explosions occur.
from the under side of the cylindars come the pistons.
They have rings around them to keep the explosion in.
They also have rings to keep the oil out of the cylindar.
On the top is a flat or rounded surface to catch the force.
On the bottom is a connecting rod.
The connecting rod joins onto the crank shaft through journal bearings.
The crank shaft joins onto the block with thrust bearings bearings.
Also on the bottom is the oil pan and, oil pickup tube and oil pump.
On the top is the head (if it's inline/straingt).
If it's a V engine, on top are the "heads".
Generally, you only have 2 heads if you have 6 or more cylindars.
A head has an assembly on top of each cylinder it serves.
Each cylinder has valve 2, 3 or 4 ports in the head.
Some valves let in air/fuel. The other valves let out exhaust.
Each port has springs, push rods, valves and rocker arms.
The cam shaft is mounted above or below depending on the type of engine. (OHC/DOHC)
The cam is a shaft that rotates and has nubs on it.
As the nub rotates, it pushes the push-rod.
The pushrod pushes the rocker arm.
The rocker arm pushes the valve.
When the nub passes, the valve springs cause it to return.
On top of each head is the valve cover.
It's just a hollow metal shell that keeps dirt out, oil in, etc.
On one side of each head is the intake manifold.
Generally, for a V engine, you have one which is between both heads.
For performance engines, you may have two separate ones.
This gakes mixed air/fuel and splits it to each intake port.
On the other side of each head is the exhaust manifold.
Generally for a V engine, one is on each side.
This takes the exhaust from each exhaust port to the exhaust pipe.
This is generally rusty looking from heat.
The exhaust manifolds may run one pipe per cylindar,
or maybe one for the whole engine, depending on needs.
The exhaust runs to the catalytic converter (hopefully).
This takes the heat and breaks down the incompletely burnt fuel.
This basically reduces polution.
Leaded fules destroy catalytic converters.
The exhaust pipe continues out the other side of the catalytic converter.
This connects to a muffler (hopefully) which reduces noise polition.
From the muffler is a short section of pipe to send the exhaust to the back or side of the vehicle.
Sometimes this has a chrome or stainless wrapper.
In racing systems, Exhaust systems are modified to reduce exhaust pressure.
This generally involves removing the catconverter and the muffler,
using wider pipes and using more pipes.
On the top end, the intake manifold will need air and fuel.
Air comes in from a pipe.
This passes through a filter to block dirt/dust/golfballs.
This may have an air pump (supercharger), a scoop, and/or a cooler.
Anything to get higher mass of air into the intake = more power.
Fuel comes in through either injectors or a carburator.
A fuel injector is a series of hoses and nozzles.
They use a timing system for the squirts.
This is commonly computer controlled (EFI = Electronic Fuel Injection).
Computer control allows more precise adjustment of how much fuel is sent.
Carbs use mechanical means to mix fuel and air.
The fuel and air are sucked in by the engine vacuum.
The fuel and air are accelerated by a "venturi cluster".
This is based on the concept that a decrease in pressure = an increase in velocity.
The cluster is really just a suspension frame which helps mix the air and fuel completely.
A carburator has an acceleraor pump.
When you push on the gas, it squirts more fuel to help it start acceleraing.
The fuel pump will keep a steady flow of fuel based on the engine speed.
There are also turbo chargers, which use the force of exhaust gas on a turbine to help engine perf.
I'm not very familiar with their exact design.
They get hot and cook the oil that lubricates them.
It is recommended to have a turbo-timer or similar.
This is a small pump which keeps oil circulating through the turbo until it's cool.
This way, when you turn off the engine, you don't roast the oil into grit and varnish.
Now, one thing to consider, now that you have a rebuilt head is that it is likely that the old head was leaking pressure. As such, the new one will likely leak less pressure. If the head wasn't manufactured defectively, chances are the rings have worn into the cylindar a bit by now, and the increased compression will blow a little fire past the rings.
What this means is that you may burn oil faster than you did before. When oil burns, it turns to grit which sands away the insides of the engine causing faster wear-out, decreased efficiency (aka more spent at the pump) and increased heat (which adds to both of the above)
I would make sure you change your oil a little early from now on instead of a little late. Also, I'd make sure the coolant is still green. Water isn't good and tap water is worse. If there are floaties in your radiator fluid, or if you haven't had it flushed in a few years, have that flushed out.
If you've been using tap water, there might be crusties all over inside from the minerals binding to the metal inside. This makes the radiator not work very well. If there's already a flush kit installed, you could drain the fluid (engine cold), then flush it out with clean water (hose/tap is OK here) and drain it. Then put in a cup or two of vinegar, and top off with hose/tap water. Let it sit overnight. Then drain and flush until there's no vinegar smell. Then refill with distilled water and the proper coolant for your car in the proper proportions (listed in the car book, gotten from the dealer on the phone, or on the bottle of coolant).
Things not covered include timing chain, distributor timing advancement, harmonic balancer, and more.