"so let me see if i understand..
wblock is a dwg file consists of many blocks . is that right?"
Even easier: wblock is a dwg file. like any dwg, it can contain nothing, or a thousand different types. Typically, it;'s a "subset" of the original dwg. Say for example, your contractor wants a dwg to do some dirt #'s on. You don't need to send him everything that'd be on the construction dwgs. He needs basic grading info. You could create a "wblock" that would contain this smaller subset (info and objects relating to grading).
Yes, you purge block definitions out of your drawing, providing of course, they're not in use 🙂
"i am still seeing some redundant blocks when i go to insert/block/browse. where are these blocks and how do i delete them?"
It depends on how the blocks were created.
For instance, say I create a block to represent a mahole. I create the first block and call it MH. It's a single circle.
I later realize I'll need a storm manhole and a sanitary, so I decide to create two more blocks.
I insert MH and add a "S" in the middle for sanitary. I then create a new block called SMH that consists of the block MH and the text object.
I can now erase all insertions of MH, but the block MH will still show up since it's "nested" in SMH.
I'm sorry to offer such a long winded explaination, but it is a fairly "deep" subject.
are we getting closer?