Matt 16:18 - ........ I will build my church and the gates of Hades will not prevail against it.
These words of the Lord Jesus Christ are promising us two things. He will build his church. Note that it is HIS church. Church means the people who belong to him by receiving him into their hearts as Lord and Saviour, believing that he died for our sins, was buried and rose from the dead the third day.He builds his church by giving us the Holy Spirit to empower us to witness for Christ.
Hades means the unseen realm and it refers, in this context, to Satan and his demons. The gates refer to the places where decisions were made. This means that the plots of Satan will never prevail against the Lord Jesus Christ and his building project. That is good news!