This scene basically acts as a way of giving information to the audience about what has happened to these two characters as Lennox is shown talking to a Lord who tells him the latest information regarding Malcolm and Macduff, and the increasing opposition that is being mustered against the rule of Macbeth in England. We are told that Malcolm has been received in the English court by King Edward, and that Macduff has gone to join him to help him raise up troops to fight against Macbeth's occupation of Scotland:
Is gone to pray the holy King, upon his aid
To wake northumberland, and warlike Siward;
That, by the held of these (with Him above
To ratify the work), we may again
Give to our tables meat, sleep to our night,
Free from our feasts and banquets bloody knives...
Thus this scene tells us of the opposition movement that is being raised against Macbeth and his tyranny, and how it is centred around Malcolm in England, and how Macduff has gone to join it to try and give new impetus to the cause.