National Instrument 43-101 (NI 43-101) is a rule developed by the Canadian Securities Administrators (CSA) and administered by the provincial securities commissions that governs how issuers disclose scientific and technical information about their mineral projects to the public. It covers oral statements as well as written documents and websites. It requires that all disclosure be based on advice by a "qualified person" and in some circumstances that the person be independent of the issuer and the property.
 
A qualified person (QP) as defined in NI 43-101 as an individual who:
 

a) is an engineer or geoscientist with at least five years of experience in mineral exploration, mine development or operation or mineral project assessment, or any combination of these;
b) has experience relevant to the subject matter of the mineral project and the technical report; and
c) is a member in good standing of a professional association.

NI 43-101, together with its Companion Policy 43-101CP and Form 43-101F1 Technical Report can be downloaded from the Ontario Securities Commission (OSC) website (http://www.osc.gov.on.ca/Regulation/Rulemaking/Current/rrn_part4_index.jsp) . You will need to scroll down the page to 43-101, 43-101CP and 43-101 F1 Standards of Disclosure for Mineral Projects and then view/download the files from the appropriate links there. 

Laymen definition of standard categories of resources:

• Proven & Probable (P&P): These are bankable mining reserves – basically Measured and Indicated resources with established commercial value. This is what most producers actually mine.
• Measured & Indicated (M&I): These higher-confidence categories have been sufficiently drilled to establish their geometry and continuity reasonably well.
• Inferred: The lowest-confidence category, based on just enough drilling to outline the mineralization. In many cases, Inferred resources (as the name suggests) are really just guesses at what might actually be there.