From the manual

Attack in the middle

Attacking in the middle (AIM) means your team focuses on attacking down the centre of the pitch, at the expense of attacks on the wings. In other words, you trade wing attacks for attacks in the middle.

Advantage: Around 15-30% of your wing attacks will be converted to attacks in the middle.

Disadvantage: Your wing defence (on both sides) gets somewhat worse.

Relevant Skills: The total passing skill of all your outfield players determines your AIM tactical skill.

Whenever an attack is switched from the wings to the middle, it is shown in the match report.

Attack on wings

Attack on wings (AOW) works in the same way as "Attack in the middle", only in reverse; meaning you trade middle attacks for attacks on the wings. As there normally are less attacks in the middle than on the wings, you convert percentage-wise slightly more of them.

Advantage: Around 20-40% of your middle attacks will be converted to wing attacks.

Disadvantage: Your central defence gets somewhat worse.

Relevant Skills: The total passing skill of all your outfield players determines your AOW tactical skill.

Whenever an attack is switched from the middle to the wings, it is shown in the match report.