what is the dirrerence between -part and board_part

[ustc115864]

CMD1: create_project lab1 ./lab1 -part xc7z020clg484-1

CMD2: set_property board_part xilinx.com:zc702:part0:1.4 [current_project]

In CMD1,I can see My vivado(2018.2) has create a project by xc7z020, so why I still need board_part? I can't find answer in  ug835, so I come here to ask, thx

[preusser]

Setting the `board_part` provides Vivado with much more information than just the FPGA device. E.g. it allows you to specify your pinout in terms of somewhat meaningfully named `board_pin`s rather than pin coordinates.

[vsrunga]

Hi,

Second command applies board part to your current project and enables the project to take advantage of platform board flow.

This is equivalent to choosing a Board during project creation rather than a part.

Going through UG895 Platform Board Flow topics may help ..