Chapter I - The ChainModern chains are sealed units with preinstalled factory internal lubrication. Some are of the "endless" variety and must be assembled/disassembled using special tools for replacement or when required for other maintenance prcedures.
They come in different sizes or "pitches" and are specific to an application.
O-Ring:
These are the seals that retain the factory installed "grease" internally. Preserving these is part of the goal of proper chain maintenance.
Masterlink:
This is the part of the chain that allows you to disconnect it from itself. There are three types; Riveted, Slip-fit clip type, and Press-fit clip type.
Only the "Slip-fit clip type" is easily roadside friendly.
The "Press-fit clip type" can be dealt with on the side of the road, but it's a pain in the ass.
The "Riveted" type refers makes an endless chain and requires special tools to work with. It can be disassembled and assembled with common hand tools and workbench, but it ain't fun and it won't work as well or be as safe.
Lubrication:
This is a highly contentious topic. There as many theories as there are riders, but The following is universal.
No matter what you use, use it often and keep your chain as clean as poosible. There are two basic types of lube; Oily, and chain "wax". Manufacturers recommend "oily" as in 80wt to 90wt gear oil brushed onto a clean chain usually every 300 to 400 miles. Some use WD40. That might be OK for cleaning a chain, but it ain't gonna lube it and some say it will deteriorate the o-rings that seal the chain.
Chain "wax" is a class of spray on lubricant that won't fling off the chain and applies in a somewhat less messy manner than "oily" libricants do. I hate this stuff. It does nothing to prevent corrosion of the chain plates and your chain will look like shit right quick.
The Best Solution is to install an automatic lubrication system such as a "Scott Oiler" or somesuch.
The following manufacturer's link has videos of chain assembley and disassembley.
Chain Stuff