RPGGamer It's absolutely not the same app but both access the IE core when browsing. Internet explorer is practically a modified Windows explorer window with standard settings to browse the internet and use the IE core.
About Windows explorer. It can be interpreted as two different things...
Windows explorer - The filebrowser
Explorer - The GUI shell
I've tried many of the replacements but here are the one's I consider the best.
Windows explorer - Directory opus
Explorer - Xoblite (Other alternatives are for ex Aston shell, bb4win, bblean, and so on)
There is another very popular GUI shell replacer but I can't remember it. Check Neowin. They got loads of that info.