compat-mode

Hi
I want to Know "compart-mode" mean.
when I changed "compat-mode"　Characters are misaligned.
is that what it is

Can anyone help me to enable it, I will be very pleasure, thanks.

before

　<site url="www.sample.com">

 　<compat-mode>default</compat-mode>

　　<open-in>IE11</open-in>

　</site>　
↓
after

　<site url="www.sample.com">

　　<compat-mode>IE8Enterprise</compat-mode>

　　<open-in>IE11</open-in>

　</site>

memo:

https://learn.microsoft.com/ja-jp/internet-explorer/ie11-deploy-guide/enterprise-mode-schema-version-2-guidance