“He that speaketh in an unknown tongue edifieth himself; but he that prophesieth edifieth the church.”
1 Corinthians 14:4

He says the person who speaks in tongues does to himself what the person who prophesies does to the church:
“But he that prophesieth speaketh unto men to edification, and exhortation, and comfort.” 1 Corinthians 14:3
The one who prophesies speaks to men towards the purpose of edifying, exhorting and comforting them, the one who speaks in tongues speaks to himself towards the purpose of edifying, exhorting and comforting himself.
He is built up and improved when he speaks in tongues, he is exhorted- receives revelation and direction when speaks in tongues, he receives comfort when he speaks in tongues- amazing! The word had said:
“Now we have received, not the spirit of the world, but the spirit which is of God; that we might know the things that are freely given to us of God.” 1 Corinthians 2:12
When we speak in tongues, revelations from God’s word is imparted to our spirits and we are exhorted and we are taught, and then in the church, if we have the interpretation of our tongues we can teach others also:
“Yet in the church I had rather speak five words with my understanding, that by my voice I might teach others also, than ten thousand words in an unknown tongue.” 1 Corinthians 14:19