The Toronto Real Estate Board has a very useful section in its website that features the latest versions of standard forms used in residential and commercial real estate transactions. These are explained in plain language. Visit this link to gain access to all of them.
Let me highlight the most commonly used RESIDENTIAL forms:
The Agreement of Purchase and Sale is more commonly known as the OFFER.
I always try to explain all of the forms that my clients sign to make sure that they know what they are committing themselves to. You should never sign anything that you do not understand.
Reading through these forms and their explanations is a good first step to understanding what it is that you are signing. Of course, consulting a lawyer and your real estate agent is also highly recommended.