On your trading platform you will observe Quotes like this
EXAMPLE of USDZAR
when you buy quotes differ compared to when you sell. this is because Brokers edited the quotes so that they can charge you commissions for using their services.Both these buy and sell Quotes are higher than the original Quotes set by Banks. Banks set Quotes, then Brokers Modify the quotes.
Original Quotes
Banks says 1 USD equals to 17,10. but broker says 1 USD equals to 17.1233 when i sell and is 17.1433 when i buy
Calculations
Sell price - original price
17.1233 - 17,10 = 0.0233
the 0.0233 is commission for brokers when you choose to sell. it will differ when you buy.
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selling and buying price has more decimals than original price. those decimals are called pips.