Essentially the system by which the CPU teams made their decisions.
It tracked every significant position on the team (QB1, QB2, HB1, HB2, etc.) and listed which players in the league or in the upcoming draft by who would fit best their for your team. There was also a list of the team's greatest needs. So it would weigh needs vs. available players and make decisions based on that.
If you were, say, 49ers entering this off-season, it would like something like this-
QB1
1. Jay Cutler, available via trade
2. Matthew Stafford, available via draft
3. Shawn Hill, on team
If QB was a high enough need (and this depends on the team philosophies), the CPU team would probably explore a trade for Cutler... if the value was right, it'd make the move. If not, it'd look at the draft and see if Stafford is available, and if there isn't another player who's better and at a greater need position. If he's not available or there's a greater need that can be filled at that spot in the draft, the CPU would stick with Hill as it's #1.
Despite the occasional weird trades during the draft (occassionally a team would trade out of a draft spot, only to use the exact same picks it had just acquired to move back up into the next spot), overall absolutely the best CPU AI I've ever seen for a franchise mode.
Of course, it wouldn't be nearly as good without team philosophies, that really made the whole thing go. That's what ensured teams went for players that fit their system and their current goals (rebuilding vs. competing now, mobile QB vs. Field General, etc.).