You can be detained by immigration for many different reasons and a detention review may be required. For example, if your status has expired and immigration believes that you are either a flight risk (unlikely to appear for removal) or if you are a danger to Canadian society, immigration will detain you at an immigration holding centre until you are either released or removed from Canada.
You can be released on a bond and with conditions, meaning that, someone close to you will give money to immigration to guarantee your cooperation with immigration. Should you fail to appear for removal or fail to meet the conditions, immigration will not return the money to your bonds person. A bonds person would be someone in your life who is either a Permanent Resident of Canada or a Canadian citizen, who has known you for a while, is gainfully employed, has the finances to provide a bond and is able to have a positive influence on you, and someone who will be able to assist you in cooperating with immigration during your time in Canada.
You have a right to a detention review to discuss your potential release 48 hours following your detention. If you are not released, you will have a detention review 7 days later and then once a month unless you or your lawyer makes a request to have one sooner.
Having a friend or family member in detention is quite an ordeal. You can contact our office if you have a loved one detained and you wish to assist.
Here are some additional resources to help you address refusal or detention review in Canada