There are training courses several weeks long conducted by CSI that covers just the basics. I took it a very long time ago and should take a refresher but I'll try to condense the concept of specifications for you without getting too lengthy.
The project manual, or spec book, is part of the entire building package which is refered to as the Construction Documents which also includes the drawings, contract, and eventually approved shop drawings and change orders. The Project Manual contains two main sections, the front end and the technical specifications. The front ends describe project basics such as the form of contract, use of the site, basis of award, requirement and condition of payment, etc. The technical specifications are usually divded into 15 main sections and these describe in detail the various components of the project. Each technical specification is divided into thre parts consisting of Preparation, Products, and Execution.
The Product section describes the particular building component and is
generally selected by the designer. Say in the case of concrete, this is
where you tell the bidder what strength of concrete you need for each
element and additional properties required like high early strength or air
entrainment.
There are two major philosophies of specifications. One is generally called
performance specs and allows the contractor more leeway in how the end
result is achieved. The other method is more of the traditional approach
where you tell the contractor the exact product or mix design that will be
accepted. Most of the information should come from the designer but
there are some lazy building professionals who cut and paste one
manufacturer's spec and try to convert it to a performance specification.
Lots of reasons not to do this, the main one being that a manufacturer will
deliberately write a specification that only their product will satisfy.
Front ends should be job specific and generally is driven by the Client. Governent agencies usually have very detailed requirements concerning bidding, schedule, contracts and payment.
So I hope this is enough to digest for awhile
"If you are going to walk on thin ice, you might as well dance!"