match tag and this scenario

Route map is set by using match and set commands.
match command specifies criteria what must be matched.
It makes sense for me if I have got for instance these two type of configurations :

Code:

 
ip as-path access-list 15 permit _254$--->condition
route-map STOP_TO_MYNETWORK deny 10
 match as-path 15-------here match happened to predifined condition

or

Code:

ip prefix-list DENY_TO_AREA seg 5 permit 132.1.0.0/16--->condition
route-map WANT_TO_Prevent deny 10
 match ip address prefix-list DENY_TO_AREA -------here match happened to predifined condition

But I get confused with the one below :
http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cg/hirp_c/ch15/hroutma.htm
Here I can not find predifined condition

Code:

route-map tag-filter deny 10
 match tag 777,,,,there is no predifined condition to match !!!!
route-map tag-filter permit 20
!
router ospf 1
 router-id 10.0.0.2
 log-adjacency-changes
 network 172.16.2.1 0.0.0.255 area 0
 distribute-list route-map tag-filter in

Any clarification ? Thanks.