Bifold doors are the most popular choice for reach-in/wall closets. This type of door is available in many styles and finishes finishes from wood, glass, metal, louvered styles, and more. The reason it is so popular is that it offers one of the the largest unimpeded opening to the closet of any door style. The only one that offers a greater opening is the pocket door.
When bifold door are fully opened, the door panels fold up in accordian fashion and stand on the sides of the door opening. This obscures a small amount of storage space on the edges of the closet. For this reason, you should never place closet drawers against the back wall on the sides of the closet. If you do, you risk having the drawer bump into the bifold door. This would prevent it from opening properly. Instead, place your closet drawers in the middle of the wall when the closet uses bifold doors. This layout allows full access to open the drawer.