The word “herald” is used to talk about a person who proclaims or announces a message from a king or other ruler. A herald says the things that the king or ruler wants the herald to say. The herald announces these things to the people the king rules.
God chose the apostle Paul to be a herald of the gospel (see: 1 Timothy 2:7; 2 Timothy 1:11). Noah was a herald of righteousness (see: 2 Peter 2:5). That is, Noah told the people about God’s righteousness. The king of Babylon sent a herald to loudly proclaim a message to the people (see: Daniel 3:4).