Akismet is an anti-spam measure
Akismet is a great way to protect your comment section from spam.
If you have a personal or non-commercial site, you can get Akismet protection for free.
Akismet Settings: With the Akismet plugin installed, you can find the Akismet settings under Settings->Akismet or with Jetpack, Jetpack->Akismet.
Some users use Akismet for purposes other than comments. If you don't want Akismet protection for comments, you can disable this.
If you want to skip Akismet protection for logged-in users, you can disable this option.
With comment editing, each edited comment is checked for spam when Akismet is enabled.
You can disable this option if you want Akismet protection turned off for edited comments.
You can disable Akismet from checking any new pingbacks or trackbacks.
Gravatar is a service for hosting user avatars. If a user has a valid Gravatar, they can skip the spam check.