The settlement period is the length of time between the trade date and the settlement date. This time is given to the parties involved in the transaction to complete administration and payment.
For most nominee trades money will be credited to your trading account (for sales), or taken from your bank account (purchases) within 2 working days from the date you place a trade. This is referred to as "T+2 settlement". For example, if you deal on a Monday, settlement will be on a Wednesday. If you deal on a Thursday, settlement will be on a Monday.