Soundings -  Page 1
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NOTE 
Not all charts use quite the same axes nor the same colour schemes and units.
 

These diagrams are theoretical, simplified Skew-T's .

It might be worthwhile printing out these pages.

If you experience difficulty, best method might be to use Print Screen key top right of keyboard.

Then paste into eg 'Word'
millibar (hpa) pressure levels are on the left in blue
Surface pressure is normally around 1000 to 1025 mbs
Each mb corresponds to about 30 ft (in lowest part of the atmosphere)
850 mbs is about 5,000 feet an important level 
700 mbs is about 10,000 feet
500 mbs is about 18,000 feet
300 mbs is about 30,000 feet (cirrus level)
Wind arrows (and numbers) are down the right hand side
short dash is 5 knots   long dash is 10   triangle 50 knots
The direction is shown by the arrows.
Difference between true and magnetic can be ignored.
In this example :
At 500 mbs triangle and short dash means 320°/55 kts
At 30,000 feet (300 mbs) the wind is approx 340°/75
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Temperature lines
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The red arrows point to numbered red diagonal lines.
These are temperatures.  eg, 0, 10, 20 etc
The red line that wiggles its way up the page is the environmental lapse rate line (ELR) ie a plot of temp with height.
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It can be seen that the environmental line meets the bottom horizontal 1000 mbs line roughly midway between the two red diagonal lines marked 10 and 20
This is the surface temp of around 15°C
(before any heating raises it later).
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Now follow the ELR up to the 850 mb level.
Here the temperature is about 3°C
At the 700 mbs level, it also happens to be 3°C in this example, ie there is an isothermal between 850 & 700 mbs.
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At 300 mbs the temperature is -38°C
Moisture content

Yet more lines
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Reminder - the red line is the ELR (environmental lapse rate)

The green line represents the dewpoint against height. 
Thus at 10,000 feet, the dewpoint is -22°C.
At the baseline, it is 8°C, ie surface dewpoint 8°C

The dewpoint is the temperature at which the air can hold no more water vapour, ie it is saturated.
Surface dewpoint is of major importance.

On the real sounding on the next page, the dewpoint line is not green, but is a the solid line on the left.

 These two arrows point to brownish/red lines .
These indicate the mass of water the air can hold at various temperatures.
For example the arrowed example on the right can hold 12 gms of water/kg of air.
In the colder air on left, it is much less at 3 gm/kg air.

At the surface dewpoint (green line intercepting base), the mass of water the air can hold at that temp is indicated.
As that air rises in a thermal, it expands, cools (3°/1000) until it becomes saturated and cloud forms.
But - and this is important - the total water the air is holding has not changed from that it held at the surface.