В чем разница между Sign in и Sign on ?Пожалуйста, приведите примеры.

We use "sign in" a lot more. We use "sign in" to also mean logging in (ロギング) to Facebook or Instagram or to sign in when we write our name down to show our attendance at an event.

Example: Where do we sign in for the marathon?

We use sign on to mean logging onto the Internet in general or, in business, if someone agrees with an idea or project, you can say they "sign on" to it.

Example: I think my computer is broken. I can't sign on to the Internet.

Example 2: "What does Bob think about the project?"
"He thinks it's a good idea. He agreed to sign on."