You mean 보내다 and 발송하다. right? They are the same having a word"send" in meaning. However 보내다 is more used than 발송하다. And 발송하다 is only for sending letters or goods, and something packed like pacels while 보내다 is more widely used with people,things,love and anything you want to send. Ex) 상품/편지를 발송하다. 사람/편지/꽃을 보내다. 발송,this word from chinese characters,发送 + 하다,do = 발송하다,send