This is the 29th most frequent Persian word.
خواهد
"خواهد" means "will" (used to indicate future tense) or "wants" depending on the context.
The word 'خواهد' here functions as the future auxiliary verb.
او کتابی خواهد خرید.
He/She will buy a book.
The word 'بخواهد' (a form of 'خواهد') here expresses desire or want.
او هرچه بخواهد میگوید.
He/She says whatever he/she wants.
The word 'میخواهد' (a compound with 'خواهد') expresses intention or desire.