t is equivalent to the time period, for which the amount is borrowed or invested.
Explanation:
The equation A=p+prt, represents amount receivable / payable A, after a period of t years, when a principal amount p is invested / borrowed at an annual (as time is in years) simple interest rate of r. Note that prt represents the simple interest.
As such t is equivalent to the time period, for which the amount is borrowed or invested.