You get contribution room for every year that you are 18+ and a tax resident. Money goes in post-tax; withdrawals of principle and growth are tax-free. Withdrawals can happen at any time with no penalty; you get the contribution room back in the following year.
Right now Canadians get $6000/year of contribution room; anyone who's been in Canada since they were introduced in '09 has something like $63k of contribution room accumulated. $6000 is a tangible number for a teenager with a part-time or summer job, and the lack of withdrawal penalties means that the account doubles as an emergency fund (which is what you should be doing with your first dollars if you go by r/personalfinance's chart).
Then again, the Canadians also don't have the whole "savings accounts are limited to six withdrawals" nonsense.