The Canadian Charter of Rights and Freedoms is, essentially, a bill of rights for the Canadian people. It specifies what sorts of things the government of Canada is not allowed to do to its citizens. This means that the Canadian Charter of Rights and Freedoms is an example of one part of the rule of law.
The rule of law is, among other things, the idea that the government must abide by a set of rules and cannot simply do whatever it wants to the people. The Charter is a good example of this idea. For example, Section Fifteen of the Charter tells the government that it must not discriminate against any person one the basis of things like race, sex, or ethnicity. The government, even though it makes the rules and has the power, is not allowed to do this sort of thing.
So, the Charter of Rights and Freedoms is an example of one aspect of the rule of law.