Next to the stars, which tell you the quality of the host in terms of the possibility to get the file downloaded (4 stars indicates I high possibility that you'll get the file from this/ these hosts), you will see a number. This number tells you how many hosts have the same file (i.e. name, size & type).
But be careful, some files may show up with hundreds of hosts; stay away from them, those are faked files which you'll never be able to download.
Hash(tree) actually talks about the "signature" of a file. Each file has its unique signature (i.e. hashtree) with which it can be identified. Limewire will collect the information of the hashtree to use it when you download, telling LW which part of the file you have already and which are still missing.
If you want to know more, read here:
http://en.wikipedia.org/wiki/Hash_tree 