When I try to "Get Track Names" or "Get Album Art," the wrong info or no info is retrieved

Question

I'm using the latest iTunes and Lion OS.
I have many songs from long ago (not downloaded from iTunes) which have incorrect album names, etc., and I want to clean them up, but when I enter the correct info and select "Get Album Art" or "Get Track Names," either nothing is found or the incorrect information is returned, respectively.
For example, I have a song:
Artist: James Taylor
Album: Greatest Hits
Name: Mexico
It does not have the associated Album Art, nor does it have the rest of the information like Track, Year, etc.  It just has the Track Name, Album Name and Artist Name.  I want to update this to show that it is from the original Album, "Gorilla," so I right-click and select Info, and I fill in the Album Name as "Gorilla." When I right-click and select "Get Album Art," it tells me: "Artwork for "James Taylor - Gorilla" could not be found - though it exists in iTunes. When I right-click and select "Get Track Names," the item is updatd, and now it reads:
Artist: America
Album: Mellow Rock Hits Of The 70s: Summer Breeze
Name: A Horse With No Name
When I rename everything to "James Taylor," "Mexico," and "Gorilla," and select either "Get Album Art" or "Get Track Names," I get the exact same thing: no album artwork found, and it renames it to America.
What is happening?  What am I doing wrong?  Do I have the wrong expectations of the two right-click options?

Answer 1

I don't think CDDB and iTunes Store is the same.  The CDDB gets information for CDs only (not collections of tracks made from a CD) and uses CD features such as track lengths (exact, which could be modified by a fraction of a second when you make a MP3) track count, etc. It doesn't use any information such as artist, track name. From what Mike Johnson12 was saying it seems that ITMS uses the base tag information to identify the track fully.
I have never used iTunes Store to label a track so I can't provide information there. I have no idea what criteria it uses, but for other id3 tag application and iTunes, by "exact" we mean exact.  Letter case is important, and I have even found that sometimes font can make a difference.
For album artwork I do a Google search, then restrict the finds to images and select the best quality I can find. This is also the biggest in terms of file size so I only attach the image to one file in a track. When playing iTunes on the computer it displays that image for all tracks in that album.