A desire called streetcar

Over the years, some have expressed an interest in bringing back streetcars to Chico. After all, once upon a time, streetcar lines threaded through the heart of Chico. Some cars went all the way to San Francisco. My colleague Vince Abbate wrote more about electric trains and streetcars here.
I happen to enjoy taking mass transit, for the most part. I’ve taken rides on streetcars in San Francisco, Salt Lake City, Toronto and more. It’s a good way for me to learn about a city without getting horrendously lost in my car. Many have their advantages and disadvantages, but I imagine cost is one of the biggest factors.
There’s a certain nostalgia for the streetcar or trolley. There’s a painting of one in Chico City Plaza and there’s a bus dressed up to look like a trolley. A streetcar system for Chico would be cool, but I wonder about the practicality, cost and flexibility of a light-rail system in such a modestly sized city. Especially given the struggle about growth and how building up (or denser) seems like an unpopular option among many.
Still, it’s nice to dream and look at what other cities are doing. The New York Times recently looked at streetcar projects across the country.
Now, I would be very happy if someone could explain the difference between streetcars and light-rail transit (I imagine a Venn diagram is in order).