Home computers/laptops, internet connections, wireless - HELP!?

[Dimples]

Our current set-up: Dell desktop, cable modem, internet provider is COMCAST.

My daughter and husband just got new laptops (I have no idea what kind of connection-"things" they have though - they are from Dell, hopefully they have something ready to go?). I am considering purchasing a laptop also.

(1) Can we leave the cable modem as is and just connect the connection cable to each computer whenever we need to access the internet? Or do we have to pay for 3 separate internet connections through Comcast?

(2) If we do wireless internet at home, how does that work? (I know this can be a complicated answer, but someone who can make it succinct and VERY EASY to understand for a tech novice like me would be FABULOUS). Can all three of us access the wireless internet at the same time?

(3) Can we have 2 wireless connections and 1 "real" connection (my husband's job doesn't allow wireless on his computer for security purposes, only "real" connections - I don't know if that makes any sense)