- Residential buildings can be identified by the name of the street they're on and a number.
For whatever reason, we decided that naming streets and numbering the buildings on them is too passé, so lots of our cities use Section + Number (where the numbers carry no geographic meaning), in parallel with Street + Number, but every building is addressable using only one scheme.
Concrete example with the city of Sofia, Bulgaria - consider these two buildings  . They're both next to Vasil Kalchev street. One is a kindergarten, the other is a block of flats. Let's see what the address for each is, if you want to send a letter to them. The kindergarten is, obviously, St. Pimen Zografski street No. 5... well OK, that's the street on the other side of the building, nothing too strange; while the block of flats is zh.k. Dianabad bl. 54. The abbreviations mean literally "residential quarter Dianabad, residential building number 54". No, the building is not addressable via the street, you cannot send post to that building or locate it on a map via "Vasil Kalchev street, No. X" for any X. There are, in fact, no numbers on Vasil Kalchev street. And the residential building numbers aren't geographically meaningful - directly east of said building 54 is building 53, but directly west of it are buildings 42 and 43. There is no building 44. There are, however, 33, 33A, and 33B. They are just ad-hoc numbers (maybe with letters) that you need to have in a database, like you have the locations of streets and where the numbers on the street are geographically.
So what does this have to do with Google? Maps doesn't understand the Section+Number address system. 90% of the residential buildings cannot be found on Google maps using their official address. If I need to send my address to a friend, I can only do it as coordinates, because entering my address, the one on which I receive mail, will result in either no results, or worse - Maps will try interpreting it as a place name, do a partial match, and send you to some completely unrelated building, maybe on the other end of the city.
They're getting kind of better, because people are adding buildings to the map as "missing places", but it's still much safer to just use our local maps site. What I do to plan routes using Google Maps is first locate where the place is using our maps, then match the location on Google's. At least it has pretty good road data.
Edit: P.S. I just checked and OSM understands my address, and even shows you building numbers when you scroll around the map.