Without telling his family, Mr. Bennet visits Bingley. Back at home, Mr. Bennet teases his family by pretending to be uninterested in Bingley's arrival, only to then reveal his visit by asking Elizabeth when the next ball is scheduled and promising to introduce her to Bingley beforehand.
It was inappropriate for women to seek a direct introduction to men, so Mr. Bennet must initially act as the mediator. Mr. Bennet's visit shows that even he recognizes the importance of making a match.
Mrs. Bennet is delighted and praises her husband and his little joke. She promises all the girls that they'll get a chance to dance with Bingley.
An early sign of Mrs. Bennet's fickle character. She can snap from disapproval to approval.