The purpose of Canada PPTC 153 is to apply for a Canadian passport for a child who is under 16 years of age. This form is specifically designed for parents or legal guardians who want to obtain a passport for their child. The PPTC 153 form requires the necessary information about the child, parents, and any other legal custodians, along with their signatures. It also provides consent to the issuance of the passport and includes a section for a guarantor to verify the child's identity.