min fee release - you will automatically accept an offer of the value specified
relegation release - only if you relegate
non-promotion release - only if you don't get a promotion
foreign club - only if the offer comes from a foreign club (playing at a higher rep league? not sure on that but it makes sense)
higher divistion club release - only if the offer comes a club playing in a higher division (e.g. top flight buying from second tier
league club)
wage rises and drops - self-explanatory
landmark goal bonus - you'll pay the amount if the player nets the goals specified in one season
extension after league games - if a player makes the specified amount of appearances in the final year of his contract, it'll be renewed for 1 year automatically
match highest earner - guarantees that the player will recieve the highest wage in the club. So if you sign a new player and his wage is higher than that of the guy with a MHE clause, the latter's wage would automatically rise to match the new highest wage in the club
wage after league games - player's wage rises automatically to the specified amount after the specified number of appearances