Railway, light railway, Tramway, what is the difference?

[ericmark]

I know there was a light railway act, speed limits, enclosure of moving parts, use of platforms etc, but some systems seem to encompass all. The railway engines which ran across roads had bells, as well as whistles, but if I look at the Welshpool & Llanfair light railway, the engines look the same as any other narrow gauge engine except for the bell. And I look at the modern Blackpool tram, and it looks like a train to me.

I look at steam trams

and as expected all workings are enclosed. So any ideas?