What does NSString's isLike: actually do?

I'm trying to figure out what isLike: actually does to NSStrings and having trouble. Apple's own documentation is very vague:

Returns a Boolean value that indicates whether the receiver is "like" another given object.

...

The default implementation for this method provided by NSObject method returns NO. NSString also provides an implementation of this method, which returns YES if the receiver matches a pattern described by object.

It mentions a "pattern", but with some rudimentary testing, it does not appear to be using regular expressions. What exactly is the pattern format in this case?