The format proposed by the IGF is this (quoting the IGF's language):
"A 72-hole individual stroke play for both men and women, mirroring the format used in golf's major championships. In case of a tie for either first, second or third place, a three-hole playoff is recommended to determine the medal winner(s)."
Very straightforward: Men's and women's tournaments, stroke play, 72 holes each, a 3-hole playoff in the event of ties.
Now, here is how the IGF proposes selecting the field for such an Olympic golf tournament:
"A field of 60 players for each of the men's and women's competitions, utilizing the Official World Golf Rankings as a method of determining eligibility. The top 15 world-ranked players would be eligible, regardless of the number of players from a given country. Beyond the top 15, players would be eligible based on world ranking, with a maximum of two eligible players from each country that does not already have two or more players among the top 15."
The key points are that each tournament (men's and women's) would have a field of 60 golfers; and that players in the Top 15 of the men's and women's world rankings would gain automatic entry.
Outside of the Top 15, players are selected based on world ranking - but only if no more than two golfers from a single country are already in the field. This stipulation is meant to diversify the field, ensuring that many different countries are represented (it's the Olympics, after all).
Assuming the IOC adopts the IGF's recommendations (and that those recommendation don't change prior to the 2016 Olympic Games), we can deduce what the Olympic fields will look like.
Let's use the men's world rankings from mid-August, 2009 (the time at which the IOC announced golf's inclusion), to give some examples. The Top 15 players at that time were:
1. Tiger Woods, United States
2. Phil Mickelson, United States
3. Paul Casey, England
4. Kenny Perry, United States
5. Steve Stricker, United States
6. Sergio Garcia, Spain
7. Henrik Stenson, Sweden
8. Geoff Ogilvy, Australia
9. Stewart Cink, United States
10. Padraig Harrington, Ireland
11. Jim Furyk, United States
12. Vijay Singh, Fiji
13. Lee Westwood, England
14. Martin Kaymer, Germany
15. Camilo Villegas, Columbia
Those 15 players would be automatic qualifiers. There are six Americans among those 15; they all would get in, but no other Americans would qualify. Why? Because players outside the Top 15 get in only if their country doesn't already have two representatives.
Likewise, Paul Casey and Lee Westwood would be the only golfers from England, Scotland, Wales or Northern Ireland who would qualify, because they give the Great Britain/Northern Ireland Olympic team its two representatives. (Note: Northern Ireland golfers have the option to compete as part of the Ireland team.)
Henrik Stenson would get in, and fellow Swede Robert Karlsson, ranked No. 17, would complete the Swedish Olympic golf contingent.
No. 16 in the rankings, from this example, is American Anthony Kim. Sorry AK, you can't play - there are already more than two Americans in the field. Same goes for No. 19 Sean O'Hair (USA), No. 20 Lucas Glover (USA), No. 21 Ian Poulter (Great Britain), and so on.
As you can see, many highly ranked players will be passed over. And some low-ranked golfers will get into the field, because of the 2-players-per-country limit for those ranked below No. 15.
As stated above, this is the Olympics, and organizers want to ensure a large number of countries are represented in any Olympic golf tournament. The PGA Tour said the proposed format would lead to golfers from 30 countries making up the men's field using the world rankings cited above.
We can assemble imaginary fields for the men's and women's Olympic golf tournaments, using the proposed format and field - and that's exactly what I did first in October 2009, then updated at the time of the 2012 London Games, using the world rankings in effect at that time. See the sample Olympic golf tournament fields for a more in-depth look at what the Olympic golf tournaments might look like.