It is a measure to judge how effective a pitcher is. If it calculated by taking the total earned runs a pitcher has allowed and dividing by (total #of innings pitched/9). Giving you an average number...
No, it is unearned.Actually, it's an earned run.Check Rule 10.18a of scoring:An earned run shall be charged every time a runner reaches home base by the aid of safe hits, sacrifice bunts, a sacrifice...