[est]

see the part 同期とは "synchronization".

I think users without prior IME experience may have a hard time image what is the purpose of sync or what does it do. It's a user trained Bayesian db where you can input your most used words/combinations very fast.

It's like auto-complete in IMEs or Google Suggest where you can get a list of "hints" ordered by popularity.

Baidu IME does the same, except, according to OP:

> ... sends users’ information even when the function is turned off.