Pickleball and tennis are both racket sports played over a net, but they differ in court size, equipment, and core rules. A regulation pickleball court is 20 by 44 feet (the same footprint as a doubles badminton court), while a tennis court is 78 feet long and 27 feet (singles) or 36 feet (doubles) wide.
Pickleball uses a solid paddle and a perforated hollow plastic ball; tennis uses a strung racket and a pressurized felt ball. Pickleball also has a 7-foot non-volley zone (“kitchen”) near the net and a two-bounce rule on the serve and return—features tennis does not share.
Source: Pickleball — Wikipedia (court and equipment; see also Tennis court — Wikipedia for ITF tennis dimensions).