7 Common type of engine layouts

Straight / Inline engines

All the Cylinder are in a single Row. - Smoother and Simpler to construct - As the no of cylinder increases the size is larger and can also have balancing and vibration issue Most Common is I3, I4, I5, I6, found in regular cars

V engines

All the Cylinder are place in a shape of V. - Compact Size - Lower Center of Gravity - Complicated Engine - Needs counterweight to combat - vibrations Most Common is V2, V4, V6, V8, V10, V12 found in sports cars

Flat/ Horizontal engines

The cylinders move in same direction - Better Center of Gravity - Better for Air Cooling - Lower Vibrations - Requires 2 cylinder heads and is quite wide Most Common is Flat-4, Flat-6, Flat-8, found in Toyota GR 86

Boxer engines

The cylinder move in opposite direction - Better Center of Gravity - Better for Air Cooling - Lower Vibrations - Requires 2 cylinder heads and is quite wide Most Common is Flat-4, Flat-6, Flat-8, found in porsches

W engines

All the Cylinder are place in a shape of W. - Compact in Size - Easily Balanced - Lower Vibrations - Complicated Design - Rare Engine Layout Most Common is W8, W12, W16, found in Bugatti

W engines

All the Cylinder are place in a shape of W. - Compact in Size - Easily Balanced - Lower Vibrations - Complicated Design - Rare Engine Layout Most Common is W8, W12, W16

Rotary Engines

All the Cylinder are place in a shape of W. - Produces more power per stroke - Low Maintenance engines - Lower fuel efficiency - Unreliable engines Most Common in Mazda Rx-7

I have listed 7 most common engines layouts you can find in the current market. There are lot more like X, U, H and more but those are not common in cars