The UEFA Champions League is an extremely complicated competition.  It contains several phases, some of which are single-elimination, others are league format or group format.  But, however it goes, it systematically takes about sixty to seventy clubs and makes them earn their berth in the Champions League Final, usually held in late May.

The way it works is that the main competition has 32 clubs.  These 32 clubs either qualify directly or must play their way in according to seeding by UEFA.  In the case of Germany, for example, its first two clubs automatically make the 32, while the third place club must play its way in.  Most of the smaller nations must play all their entries in.

The following are the sequences of stages from start to finish.

Qualification Rounds.  Typically played in late summer/early fall before the national competitions get into swing.  These games determine the 32 clubs in the "First Round".  Usually three qualification rounds are held, and each are single-elimination.  Teams who must play in are seeded, and they enter the competition in either the first, second, or third rounds.

• The weakest clubs face off in the first round, normally a two-game home-and-home series where aggregate goals determines the winner.

• That winner then plays a team seeded to enter the competition in the second round (a stronger club).  That winner makes the third round and faces an even stronger club.

• In the event a two-game series ends in a tie, then the 'away goals' rule applies -- teams who scored the greater number of away goals advances.  If that doesn't break the deadlock, then the teams must play some form of tiebreaker after the second game is finished (usually a penalty kick shootout).

First Round.  Usually held between September and December.  The 32 qualifying clubs are broken out into eight groups of four teams.  These groups then play six games, two against each other club in the group, one home and one away.  Teams do not play teams in other groups.  The top two clubs advance based on record, where three points are awarded per win, one per draw.  Ties in the standings during the First and Second rounds are resolved as follows:

• Goal differential.  That is, goals scored minus goals allowed.
• Goals scored.
• Head-to-head results.
• Coin toss.

Second Round.  Usually January/Febraury through March.  The 16 clubs are again broken out into groups of four, except that no two teams from the group will again be paired.  The format of the First Round is repeated to produce a final eight. 

Knockout Rounds.  Usually March to April.  The quarterfinal and semifinal rounds are two-game home-and-home series where the better aggregate advances. 

The Final is a single game winner-take-all in late May.

The groups in the First and Second Round are populated as follows.

• The clubs are stratified into pools according to their strength and/or past history in such competitions -- the top eight are in Pool A, the next eight in Pool B, etc.

• Each group is drawn, one team from each pool, in lottery fashion.

• However, there are restrictions.  One group may not have two clubs from the same country, for example.  The Second Rounds groups cannot contain two teams from the same group in the First Round.