inserts vs. sends.

Good morning guys. I've been stumbling around the DUC for quite awhile and I've learned a lot of useful recording knowledge. I have noticed that I can't remember ever seeing posts that refer to sends. In the old school days implementing sends to hardware equipment like compressors, reverbs, etc. was a simple matter whereby the use of insert cables to and from a mixer channel delivered the goods. I am assuming that the deluge of plugins that are now available is the reason for this,(?). I have several well preserved pieces of hardware that I'd love to put back into action but I'm at a loss as to how I can use them with Pro Tools 9. I'm on Win 7, 32 bit and my I/O is the Focusrite 2i4 which has outputs 1 & 2 as well as 3 & 4 which I have never used the latter. I also have my Mackie 24/8 mixer. Can any of you well educated Pro Toolists guide me in the right direction ? I am searching the PT's 9 users guide but the info there is kind of geek to me. Thanks.