2003 Ford Explorer Hi. i think the battery is dead but othe

i started my car today and it almost didn't turn over. drove it home and while driving..when I put the brakes on the radio would go off and back on.
once i got it home and turned it off i couldnt start it again. i jumped it and it started right away but the power to the windows and radio went off although the car was still running.
Any ideas what it wrong? battery or other?
Thank you, Amy Halvorsen