Figure 1: Male House Sparrow visiting a backyard in Toronto, Canada.
House Sparrows are passerines (order Passeriformes) and the namesake of this very diverse order of birds. They aren't closely related to other "sparrow" species in North America (family Emberizidae), as they are "old world sparrows" in the family Passeridae.
House Sparrows were introduced all over the globe starting around the mid-1800s, taking hold in urban and agricultural habitats. Today, you can find them on every continent away from the poles, and throughout almost all of their historic range.
Figure 2: "Distribution Map of Passer domesticus.
Dark green = [historic] range, light green = introduced range."
Their ubiquity and preference for urban and agricultural areas have placed them among the most well studied of bird species (see this book for further details). Even homeopaths want a piece of the House Sparrow!
Well studied, however, doesn't always mean well liked. If you don't know many bird watchers (aka "birders") you might not be aware of the inverse correlation between how common a species is and how excitedly you boast to other birders about encountering the species (as illustrated by this next image which I just now slapped together in R). All else being equal, rare birds are awesome, and common birds like House Sparrows are about as dismissible as they come (at least in the US).
Figure 3: Rare birds, like rare gemstones, are highly valued by bird watchers.
Common birds (e.g. House Sparrows) are about as awesome as roadside gravel.
Most places, House Sparrows are generally considered trash birds and agricultural pests. Despite their global abundance, House Sparrows are declining in parts of the UK where they are afforded a bit more respect than their overly abundant conspecifics. The declines appear to result from decreased fecundity (declines in number of fledged offspring) attributed by many to changes in agricultural land use and reduced availability insect population.
It's time for me to change terminals, so I'll leave off with this short video showing male and female House Sparrows (including a partially leucistic individual) from the UK.
(embedding disabled - click to view)