URI - the part of URL that comes after the domain (or IP/Port) name. http://curbsidr.com/guests/35/services/34/locations/33

/guests/35/services/34/locations/33 is the URI

location block allows 4 optional modifiers and a string to match against the URI:

= URI exactly matches location given

~ case sensitive RegEx match

~* case insensitive RegEx match

^~ optional RegEx match (RegEx is evaluated only if a regular match did not occur)

If no modifier is present, the match is interpreted as a prefix match.

location = /guests/35 will only match

/guests/35

location ~ /guests/35 will match

/guests/35

/guests/35/services/34/locations/33

but will NOT match

/Guests/35/services/34/locations/33

location ~ /guests/35 will match

/guests/35

/guests/35/services/34/locations/33

/Guests/35/services/34/locations/33

and so on

the tricky part is the order in which multiple location blocks are evaluated.
In general the longest most specific match wins but there are exceptions:

1. no modifier or = gives an exact match done
2. else find the longest matching prefix
3. the longest matching prefix has ^~ modifier done
4. evaluate regular expressions, first match done
5. no match, use previously stored longest matching prefix

So the order in which location block are positioned matters!