On entering the war in 1914, the British Army was faced with a shortage of '08 pattern equipment. 1914 pattern was rapidly developed as an alternative and stopgap.
Essentially, it is similar to '08 pattern but in leather. The leather manufacturers couldn't produce acceptable small, individual ammunition pouches, so in the '14 pattern set these were replaced by two large horizontal pouches on the belt. Another major difference is that the waist belt closes with an S-hook.
If you watched the television series "The Trench", then you will have seen this webbing - the participants were wearing it.