#1; motorcycle taxis are a fast and cheap-ish and are able to avoid the many potholes and bumps of which you find a lot of in cambodian roads. #2; tuk-tuks are the slowest form of transport and are open but rickety for the passengers as it is basically half a motorbike strapped to a small, open-sided carridge which is taller than a car. it is also a low-cornering capability vehicle and so is helpless against bad cambodian roads.
#3; longtail boats are small, fishing-class boats with a spinning petrol motor, on the end of which is a long metal pole attached to a propellor. they are VERY noisy when they turn on the engines and also rather fast.
#4; bamboo trains are basically wooden bedframes with bits of bamboo slat so you can sit down and 2 metal sets of wheels, 1 of which has a bicycle chain on it to attach it to a longtail engine which makes it go. it is v fast but the genious in it is that you can take it off the rails if another train comes up.