Two households, both alike in dignity,
In fair Verona, where we lay our scene,
From ancient grudge break to new mutiny,
Where civil blood makes civil hands unclean.
These lines are describing the Capulets and Montagues, who are two different families that live in Verona and have ancient history with each other as in bad blood. These families absolutely despise each other and have violent conflicts.
From forth the fatal loins of these two foes
A pair of star-cross'd lovers take their life;
Whose misadventured piteous overthrows
Do with their death bury their parents' strife.
These lines are about Romeo and Juliet, its describing how they cross paths with each other and fall so deeply in love that they die for each other in the end and when they're families are burying them, they will also bury their feud with each other too.
The fearful passage of their death-mark'd love,
And the continuance of their parents' rage,
Which, but their children's end, nought could remove,
Is now the two hours' traffic of our stage;
The which if you with patient ears attend,
What here shall miss, our toil shall strive to mend.
These last lines mean that their deaths left a mark of love, they loved each other so much that they died for each other literally because they loved each other and their deaths brought peace to each others family.
I think this chorus is used to describe both families that live in Verona who have a long history of violent conflict with each other, and the war with each other will finally be over when two lovers cross paths with each other without even knowing that they are moral enemies. The two lovers Romeo and Juliet will die in the play which leaving no choice to both families but to make peace making it the main idea in the story. This chorus also tells us some information about the story, such as where it takes place, some information about the main characters. The chorus is basically telling people what is going to happen in the play.
