How does one read the isobars in a weather map?

With a weather eye.

Isobars are lines on a weather map joining together places of equal atmospheric pressure . On the map the isobar marked 1004 represents an area of high pressure, while the isobar marked 976 represents an area of low pressure. The numbers measure the atmospheric pressure in millibars.

If the isobars a closely packed, the will be high winds.

Maps with a term starting with iso represent regions with the same value of something. Isobar applies to pressure and isotherm is the same idea applied to temperature. Maps showing constant altitudes are usually called contour maps. I did a Web search and found this article with more iso maps than you could shake a stick at.

Isobars are like contour lines on a map. They enclose regions of high pressure (hills) or low pressure (valleys). High pressure brings dry settled and sunny weather, low pressure brings cloud and rain or snow. Widely spaced isobars mean calm weather and closely packed isobars mean windy weather. Winds blow clockwise around high pressure areas and anti-clockwise around low pressure areas. Here’s an example.

Search me. I wouldn’t know an isobar from a candy bar.