[ipaddr]

It's directly in the link you provided.

"For example, an active user can be measured as a user that has logged back into her account to interact with the product in the last 30 days."

Even the marketing material is designed to confuse.

[rcxdude]

That's a monthly active user. A daily active user would be someone who logged into an account in the last day. Generally monthly active user count will be higher than daily active users, but for something like Facebook the difference is about 50% (which is what the second article linked is explaining, if you read more than just cherry-picking a line that matches your preconceptions)

And yes, that's a claim that if each user is a separate person, >20% of the world's population interacts with Facebook at least minimally each day. You can add your own interpretation about how many of the accounts are bots or otherwise duplicates, but it's a staggering amount either way.

[ipaddr]

It should be their account not her account (or his). Who writes this garbage.

[OrsonSmelles]

Alternating or stochastically varying pronouns in your examples used to be a common way to make an effort at inclusive writing, usually preferred aesthetically to constructs like `his/her'. (The style before that was basically to use masculine pronouns for hypothetical people in every single case and deny that there was anything to question about that.) I think I agree that the modern semi-standard of using `they' for examples where gender is irrelevant or unknown is strictly better, but it's hard for me to summon a lot of contempt for someone who goes with a different/older habit.