Bark & Mulch are used for a number of reasons in the garden - it helps to suppress weeds, perfect for tidying up and giving the garden beds a lift, it is great for water retention and if the right one is used, it also breaks down and adds nutrients to your garden soil.
If you are after something that will feed your soil as it breaks down you are best choosing a mulch
such as Sugar Cane Mulch, Tea Tree Mulch, Forest Mulch or Cypress Blend are all suitable.