Words like "music," "museum," and "mosaic" all trace back to some very old mythic stories about the Muses, a group of goddesses who inspired humans to create art, poetry, music, literature, and more.
A mosaic is a colorful piece of art made up of many, many small pieces of tile, stone, or glass. Mosaics can be large, small, simple, or complex, showing basic repeating patterns or realistic images of people. They can appear on floors, walls, windows, ceilings, and objects.
If something has many, many different, interesting bits or pieces, you can call it a mosaic even though it's not an actual work of art. For example, you could describe a mosaic of people's faces, a mosaic of dreams or memories, or a mosaic of stories or traditions.