Hi,
I found "Sites" in cacti 1 version, it have Latitude and Longitude but i cant find nothing about map usage of that data
What is the reason of sites ?

Sites are to group logical devices together. You can use Sites to filter for groups of devices on quite a few of the cacti tables. It can also be used with Automation to automatically create and group devices together.

As for the usage of longitude and latitude, I'd have to see if they are used anywhere else.

I'm also generally interested in understanding what else can be done with the data in sites.

In particular: Can I use the site name in my graph title (or other places if possible)?

I do not believe that we added that as a substitution variable. I would raise it as a request on the GitHub issues page.

There is a Google Maps plugin on GitHub that mostly works. I think that has something to do with it.

You can try mine

https://github.com/arno-st/map/tree/cacti-1.2x

It take the input from sites, and the device, then display on a map.
Working with googlemap and open street map

it take the lat, long of the site information, and when you add a new device it take the snmp location field to find the site, if it dosen't exist a new site is created.
snmp location has to be of that format:
Country;City;Street_Building;Floor;Room;Rack;RU;Lat;Long

if you don't have a record just put the ; one afgter the other, but if you don0't have lat and long, just remove the last field:
Country;City;Street_Building;Floor;Room;Rack;RU
OR:
;;;Floor;Room;Rack;RU;Lat;Long