Conditional execution

In the following workflow file, which jobs will start executing in parallel?

name: Parallel
on:
  push:
jobs:
  Job1:
    runs-on: ubuntu-latest
    steps:
      - run: echo one
  Job2:
    runs-on: ubuntu-latest
    steps:
      - run: echo two
  Job3:
    runs-on: ubuntu-latest
    needs: Job1
    steps:
      - run: echo three
  Job4:
    runs-on: ubuntu-latest
    needs: [Job2, Job3]
    steps:
      - run: echo 4