Charm bracelets have a long history in antiquity and were re-popularized in Victorian England by non other than Queen Victoria, known for wearing charm bracelets during her reign.
In the 19th century, charms were used to express one's personality, thus collecting charms representative of interests, hobbies and milestones. Lockets were often worn on charm bracelets, in addition to collected coins. The most highly collectible (and fun!) were "mechanical charms", those with movable parts. The fashion persists today and is the most versatile jewelry you'll ever own. Wear one stacked on a chain, or on an antique charm bracelet. Collect them for milestones or places you've visited - they're far more sophisticated than plastic souvenirs.