Verse 1: The word "*hallelujah" means "*praise the *LORD". "*Praise" means "tell someone that they are very great". "*LORD" is a special name for God. It is his *covenant name. A *covenant is when two people (or groups of people) agree. Here, God agrees to love and give help to his people. They agree to love and obey God. "His people" is "chesidim" in Hebrew. It is the people that have accepted God’s kind love. Some Bible students translate it "*saints", some translate it "God’s people".
Verse 3: The harp and the tambourine make music. There is more about things that make music in Psalm 150 in this set.
Verse 5: Bible students are not sure what the word "beds" means here. It may be something that people knelt on when they prayed.