Those that fear the Lord speak often with one another. (See Malachi 3:16.) God-fearers want to help and encourage one another. They also want to spend time together worshipping God. They desire to meditate on His name and His will.
Read again the verse. “Then they that feared the Lord spake often one to another: and the Lord hearkened, and heard it, and a book of remembrance was written before him for them that feared the Lord, and that thought upon his name.”
Those that truly love God and obey him, have their names written in a book. This is not a literal book. This is symbolism that we can understand. What it is really saying is that God remembers those that obey him, and he remembers their deeds. God will reward those who obey him.
There are other references to books of remembrance. Some of them are Exodus 32:32, Psalm 69:28 and Daniel 12:1. Notice that one’s name can be taken out of the book. In Revelation 20:12, we find that at the Judgment, books will be opened. Out of those books every person will be judged as to what he did while living.
Read the Bible. Study it. Obey God. Have your name written in the good book of remembrance. If any of this is hard to understand, ask an adult to help you.