Spread, Bid and Ask

Bid means Sell, Ask means Buy. they are alternative terms. on Meta Trade Platform they appear like that.

here USD is Base currency, and base always equals to 1. 

when you believe that counter currency will lose value compare to base currency - you choose Sell. when you believe that the counter currency will gain value you press Buy.

Spread

Spread is the difference between the bid (sell) price and the ask (buy) price of a currency pair.

There are always two prices given in a currency pair, the sell and the buy price. The bid price is the price at which you can sell the base currency, whereas the ask price is the price you would use to buy the base currency.

In above image we see USDCHF with sell price of 0.92804 and buy price of 0.92924.

Buy price - Sell Price is 

0.92924 - 0.92804 = 0,0012 spread

so spread is the difference between sell and buy price. it is measured in pips, which is a percentage.  

so we can say it is 0,0012 %. 

this is the percentage we are charged by brokers when we place trading orders