In short
The Synoptic Chart is the big picture view of pressure across the country, the highs, lows and fronts that actually create the wind you see forecast for your beach. Reading it gives you a sense of why the forecast says what it says, and what's likely coming after it.
The wind graph tells you what's expected at your location. The synoptic chart tells you why, by showing the whole weather system responsible. Once you can read one, forecasts start to make a lot more sense, and you get an intuitive feel for what's coming a few days out.
Highs, lows and isobars
An H marks a high pressure system, generally calmer and clearer. An L marks a low, usually unsettled and windier. The lines circling each system are isobars, and wind flows roughly along them, clockwise around a high and anticlockwise around a low in the southern hemisphere. Where the lines are drawn close together, expect stronger wind; where they're spread wide apart, expect it to be light.
Fronts
A line marked with triangles or half circles is a front, the boundary between two different air masses. Fronts are usually where weather changes fastest, a wind shift, a burst of rain, or a temperature drop. Watching where a front sits relative to your coastline is a good way to judge how soon a change will actually arrive.
Related reading
For a fuller explainer with more examples, see How to Read a Synoptic Weather Chart . See also How does the weather work?