ESBs are essentially more aggressive and more balanced Bitters, both in alcohol and hop character, but nothing overpowering. Color range will be similar, though leaning towards the darker end of the scale; dark golds to copper. Low carbonation. Malts tend to be more pronounced, often toasty and fruity, with maybe some notes diacetyl. And despite "bitter" being in its name, ESBs are not really all that bitter. They key to an ESB is balance.