The term sweet spot is used to describe the "most effective" zone in padel tennis. When you hit the Padel balls with the sweet spot, the stroke has the optimum efficiency.
Padel rackets with a large sweet spot in the middle of the racket have more control. Padel rackets with a smaller sweet spot at the end of the racket give you more power, so you can accelerate the padel ball faster - if you hit it right. If not, you lose a lot of control. Therefore, beginners should rather take a racket with a large sweet spot. Pro players more often take the version with a small sweet spot.
There are also rackets that have an elliptical sweet spot. These are a mixture of the two aforementioned features and represent a compromise between control and power.