Starter Battery

Hello All.
I just had my car, 2011, towed home, and the lovely tow truck driver told me that the problem was the 'starter battery'.
I had been getting gas, and upon getting back into the car, I turned it on but it would not go into drive.
I also had trouble turning it off.
Finally it turned off, and then when i started it again, which was an effort of button-pushing, I couldn't put it in drive.
And I think a couple of times it started itself.
It was like a possession!
The tow truck guy said he put some charge in the starter battery, and then he drove it up on to the truck,
He says I have to buy said starter battery and have it installed.
Does someone have advice on which one to get, please?
I don't want to show up at Pep Boys or somewhere with no idea of what I am looking for.

Thank you very much in advance for any advice.

I realise I put a pretty lame non-descriptive title.
My apologies

 

Hi Samuel.
I think it's the 12volt battery.
I have had the car for 5 years and have not changed the battery.
I drive the car almost every day.
I called AutoZone and they sold me the attached battery.
Not sure if it's the correct battery.