I've heard this is the way to measure inbound links to a website? What is the difference between the two and is there a better way besides these?
links: is not a Google Search operator, so it is equivalent to just use the word link as an additional keyword in the search. The proper operator to use is link:, not plural.
I've heard this is the way to measure inbound links to a website?
It's a way to get a feel for it.
Arguably Google would prefer that you do it via their Webmaster Tools, where you'll find it under Traffic->Links to Your Site. The
link: operator only shows you a selection of results like
site: does. (Mentioned at that previous link.) Webmaster Tools is also a better option for this as it provides some extra information like who links to you most, and how your site gets linked to.
On further review using a domain I control and so could do a better job filtering, it looks like non-existent search operators, eg
links: just get ignored and treated as a literal strings as much as possible. It'd be nice if they popped a warning message about this. But for example, if you do a search for "foo:rottentomatoes.com" you'll see results up top for things like the movie "To Wong Foo…" and the actor John Foo, plus even attempts to figure out if your search was a typo, eg. "Kung Fu Panda" also shows up.