transaction – Purpose of pre-signature field in P2WPKH

What is its purpose? 02 In this P2WPKH transaction:

01000000
0001
01
d6f3994ab779ac849996a6235699ced672fa4b8334f825a2f1fcb4081c5b0c62
00000000
00
ffffffff
02
1027000000000000
16
00140429fc6e543ff7b4b75d0c6a60013c125827aa66
5716040000000000
16
00145951ac8720b1865ba633d19eaa6473afae7c46b3


02  -----> WHAT IS THE PURPOSE OF THIS?


483045022100b826e4123a66ab38f2e5f4ede2c50c1ce93bbfbdbdc2997a6e1ff09fe964349d022060a14f272ba521ec71f022922a855bda8827b7262ca181df755fdf42f656cc97012102e2ae4b9e9d86f03d511c4716ce3af351428201f2ff0378d00c7e097fbbbcb95
000000000