Ornaments today are associated with Christmas but the tradition of decorating evergreen trees started in 16th century Germany. Trees were first thought to be trimmed with real apples to represent the tree of forbidden fruit in the Bible and to celebrate the Winter Solstice.
It is believed that the first glass ornaments were made by glassblower Hans Greiner because he couldn't afford real apples. The trend caught on and others started requesting glass fruit for their trees.
Ornaments didn't make it to America till the American Revolutionary War and didn't really catch on till around the 19th century because Christmas trees were seen as a symbol of paganism and frivolous.
Christmas ornaments really took off and commercialized under the reign of Queen Victoria. Shops started featuring ornaments seasonally and the tradition lives on.