When you buy a GIC, you pick a term: how long the bank keeps your money. Common terms are 1, 2, 3, 4 and 5 years. Some GICs are shorter, like 90 days.
Usually, the longer you lock in, the higher the rate1. The bank pays you more for waiting longer.
Your rate is set the day you buy. If rates go up or down later, yours stays the same until the term ends.
The day the term ends is called maturity. Then you can take your money out, or put it into a new GIC at the rates of the day. Some banks renew it for you automatically if you don't tell them otherwise2, so mark the date on your calendar.
Tip. Short terms keep your money free sooner. Long terms usually pay more. A GIC ladder gives you some of both.