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The pressure gradient force explains the natural tendency for air (or any other fluid) to flow from an area of high pressure to an area of lower pressure. If you push the water in your bath tub to one end, it wont remain there. It seeks to return to level.
When it comes to synoptic charts, the pressure gradient is always acting at right angles to the isobars. That is, directly out of a high pressure system and directly into a low pressure system. If it wasn't for the effect of the earth's rotation, the wind would do exactly that.
The wind is subject to two separate tendencies. The pressure gradient and the Coriolis effect that causes it to swing to the left in the southern hemisphere. In Australian latitudes, the result is that the wind tends to follow the direction of the isobars.