Figuring out deductions and your taxes is not easy. If it was we wouldn't need accountants!
However, understanding the basics is important so you know if you're being conned.
Definitions:
Canada Pension Plan (CPP)
The amount of money you are contributing to your Canada Pension Plan. The amount in there at retirement enables you to draw a pension, which is money you have put away across your lifetime. Costs don't go away when you retire, so you need to make sure you have enough to get by each month.
Many employers also offer their own pension plans that you will contribute to as well.
Employment Insurance (EI) contributions
If you get laid off (let go from your job because there is no longer a job for you) then you can access employment insurance. While you are working, you must pay into this so that there is money if you get laid off. Many seasonal jobs such as in the resource industries in British Columbia (mining, logging, etc), or even substitute teachers, access this during the off-season. However, if an employer goes bankrupt this will also come into effect.
Taxes
There are many different types of taxes, but the one we're going to deal with here is called the income tax. It's a portion of the money you earn that goes to the government to fund roads, parks, schools, universities, emergency services, and many other parts of government. Money from this also goes back in the form of 'tax breaks' where certain things taxed are returned for fulfilling special circumstances.
