The relationship between CA/PA and Attributes goes something like this.
A players attributes are either relative or absolute meaning that they grow and decline in relation to development, training and each other or that they do not improve or alter through this manner and are attributes that do not change based upon a players growth, improvement and training etc. Whether an attribute is relative or absolute depends upon the position of that player, but in general most attributes you see ingame are relative attributes for all players.
Take for example Influence or Determination. These are not relative attributes as they do not improve or decline through natural progression and player experience. They grow and decline only through very rare ingame events.
All relative attributes, and these depend on position, are closely related to CA. Infact relative attributes are CA. CA is a measure of the current total level of ability a player currently has within all his relative attributes. As CA increases or decreases so will the available ability within all his relative attributes. However not all attributes require the same amount of CA to improve by the same degree. Improving physical attributes requires much more total ability/CA than improving technical skills by the same degree. In short the higher a players CA then the higher the total sum of all ability within all of his relative attributes, but these may be distributed in such a way that the really heavy attributes like physical attributes take up much of the CA and produce an apparently inferior player.
So a player with a high CA has a higher total amount of ability within all his relative attributes, and through training these can be redistributed to produce a superior player to one with a lower CA, but equally through training you can favour really heavy attributes and produce a player that on the pitch is inferior overall to a player with low CA. Training allows you to redistribute CA amongst relative attributes and is an essential part of making sure a player with high CA really is a superior player on the pitch.
PA is simply a theoretical maximum limit that CA can reach. Very often CA will get nowhere near PA, and even with the best development strategies and best coaching and best match experience will often peak just below PA.