Difference between in game mechanics?

Question

So I was playing some Platinum the other day when in a battle I got the message "Yanmega avoided the attack!". What is the difference between the Pokemon avoiding it or the attack just missing?

Answer 1

When it says an attack missed, it is in regards to the accuracy "stat".
When it says an attack was avoided, it is in regards to evasion.

Answer 2

So, I'm sure you know what stats are. Two of them include evasion and accuracy.

Evasion is, according to Bulbapedia:

The evasion rate (Japanese: 回避率 evasion rate), or evasiveness, of a Pokémon's move determines its probability of missing the target.

And accuracy is:

The accuracy rate (Japanese: 命中率 accuracy rate) of a Pokémon's move determines its probability of hitting the opponent.

Therefore, if I use Double Team, for example, that increases my evasion, meaning that my chances of avoiding the attack are bigger. If I use Flash on the opponent, their accuracy decreases, meaning that their chances of hitting me are smaller.

Hope I helped :]