"The boy talks."
Pratar = talk and talar =speak. "I talk Swedish " is wrong, so talar is used for languages.
and sprak = language? since i can use sprak also in some cases as talar and pratar
Even though one might be more formally correct in different contexts, one can tala, prata or snacka svenska just fine.
They are interchangeable, but I believe most Swedes prefer to use pratar as it's less formal.
It is only one letter different than an English word, rarely used. There's a Shakespearean quote "a speaker is but a prater". I've also heard "prattle on" to mean to talk alot, though never just "prattle".