“Gospel” is a word meaning “good news”. The Bible defines it as good news about the Kingdom of God, and Jesus Christ. (Acts 8:12)
In essence it is the good news that forgiveness and salvation can be obtained through believing in Jesus Christ, and being baptised into him; and that believers will be rewarded with eternal life in a future age called the “Kingdom of God”.
The Kingdom of God will be a wonderful time of God’s righteous rule with justice for all including the poor (read Psalm 72!)
The word gospel is used in the New Testament to summarise the message of hope which the Apostles taught.