source
A gown with a train suggests formality; typically the longer the train, the more formal the gown. So what is a train exactly? A train is that extension in the back of the skirt that follows when you move. There are two types of trains: built-in and detachable. Built-ins are integrated in the actual skirt pattern when the dress is made. These are the kind that are pulled up and bustled after the ceremony. A detachable train is a separate component, not integrated in the skirt pattern. Detachables are usually removed after the ceremony, although I’ve seen them bustled every so often when brides want to keep that bustled look going for the party. source
Bustling defined is the gathering and tacking up of the train so that the bride can move around freely post ceremony. Once a gown is bustled it goes through a kind of metamorphosis as does the bride in it. There are two kinds of bustling techniques: overbustles and underbustles (French). Usually, bustling is secured with hooks and/or ribbons (narrow strips of grosgrain). Over bustling is the easiest and consists of picking up and tacking the skirt to the waist for chapel and cathedral lengths; or behind the knee for sweeps. Underbustling goes the other way—down and under, fastening to points on the under slip. Longer trains can take a combination of both over and under bustling all at once and the results can be stunning. Additional or custom bustling is done after the bodice fitting is completed. How many (more) bustle points you chose is up to you and the estimation of your alterations person. Keep in mind not every dress bustles well. Examples include ball gowns with skirts in lightweight layers like tulle or organza. The amount of layered skirts present problems. The bustling is done layer by layer which is time consuming and expensive, and you’d have to absolutely love the result to go through all that hassle. Also some gowns with sweep trains, godets or fishtails don’t bustle well. Overall, most dresses do bustle beautifully and are a joy to wear. A bustled train remains one of the most elegant and romantic elements of the wedding gown . . . .source
