trimmed means the rom is in a smaller size. (by cutting out useless empty bits of data in the rom that release groups add so it matches the required scene size) intro means that there's a intro (from the release group when you load it up.
Trimmed means that the 'junk data' at the end (in hex it is 00's or FF's, essentially blank space) is removed. A ROM (Read-Only Memory, the retail cart) is always sized to a power of 2: 2/4/8/16/32/64/128/256/1024/2048 Megabits and any unused space is filled with the 00's or FF's mentioned above. When it is dumped, a perfect copy will have that 'junk data'. For the most part it is useless, and modern trimmers like NDSTokoyTrim will remove it safely. "Independent" is the release group/person who dumped the ROM or uploaded it to the internet. A few of the more common ones are Trashman, Bahamut, and Xenophobia (who uses intros making their ROM dumps NOT clean).
Trimmed means that the useless filler data has been removed from the ROM (this may be a good thing unless you plan on patching the ROM) Independent means that it wasn't a scene group who put it on the internet, but it was a single person. Intro means that someone hacked the ROM and put their own custom intro screen into it. This is usually done by a scene group to accredit themselves, although this breaks the scene list rules.
