ip or user lock out?

I’m getting an insane amount of emails about my users and failed attempts to log on to the site. This are obviously not my users – I”m assuming it is a bot or a malicious person seeking entry … does this mean that the legiimate person can’t log in for 15 minutes after the username has been locked out – or is it the ip address that has been locked out?

https://wordpress.org/plugins/better-wp-security/