The contribution room for both TFSAs and RRSPs carries forward year after year, which means that if you do not max out your contribution one year, it is not forfeited but is cumulative year after year. To find out what your total available contribution room is, refer to your last notice of assessment.
For RRSPs, that annual contribution limit is the lesser between 18% of your earned income for the previous tax year and the maximum contribution amount set by the CRA for the current tax year.
Another significant difference between the two accounts is what happens when you withdraw money from them.
When you make a withdrawal from your TFSA, that frees up your contribution room for next year's deposits. On the other hand, if you make a withdrawal from your RRSP, the contribution room is gone.
The differences in available contribution room between TFSAs and RRSPs serves as a decent illustration of how you can use both accounts to save for your retirement: the RRSP has much more heft to it whereas the TFSA is much lighter, useful to get you started or as an added bonus.