Isn't that for sure!! OK - here are a few basic differences...
Albums are tightly integrated into the Forum code - so a single login allows anyone to view/post/upload/etc... As well - as simple as the albums appear - here is what happens on my servers... When you upload the photo, my servers/software resizes it for you, processes the picture and then adds it to your "Album".. From there - images are redrawn from my server for a clients browser - and expanded/contracted using either highslide/lightshade.. For that - again - you have "control" of your album contents integrated into your album(s) - including the ability to tag or add comments.. As well - if someone makes a comment - you can option whether to receive an e-mail notification through the Forum software...
That's Albums in a nutshell....
The Gallery is totally different - both in architecture and capabilites - and no - it is not integrated into the Forum software (although I've tried).. Gallery is all the features of Albums, except on steroids.. I use it for example - as I do advanced photography - so one of my "Galleries" is here:
http://reutterwerk.com/gallery2/main.php
The features - for me at a personal level - are far more robust - but are somewhat silly given if I only wanted to "share" pictures amongst a closed forum.. That - coupled with the separate admin aspect..
As well - I also run host an altogether different Album/Gallery technology on one of my other sites - WHICH is integrated into the Forum login/software called Photopost - but again - most folks on that forum use the Albums - as they are simple.. To see Photopost - click here:
http://reutterwerk.com/photos/
But again - I'm the one left coding and supporting these architectures - and for most users - both Gallery and Photopost are difficult to use for an occasional user...?
Hope this helps!
John D.