There are many musicians who play in bands without rehearsing - they can do this by having a good knowledge of harmony and of musical structures. They would also use a chord chart like the example shown below.
This chart gives all the information needed to play a tune
all the way through by " comping " or " busking " to the
chords as written.
It also tells the player how many times and in what order to play the sections marked "A" and "B" These sections in this example would be "A" = verse + chorus and "B" = bridge.
Because these sections repeat writing the chords like this is a kind of shorthand making it possible to put the whole tune on one sheet.
This particular tune has only two sections but some more complicated pieces might have three or even four - these would be designated as "C" and "D" sections.
The symbol in bar 4 means repeat previous bar.The last bar in the "A" section has an alternative underneath it with a number 2 - this means to play this chord every second time round.
Again this is commonly used shorthand to save writing out the whole sequence again with one different bar.
In the rock world you might not need this style of chord sheet but in the jazz world it's a common approach - and actually writing any tune out in this style can help to get a good overall picture of the music.
Write out any tune in this style.