If you’re 17 years of age, for example, the law does not prohibit you from engaging in consensual sexual activity with your 17 year old boyfriend/girlfriend however if the two of you agree to take a nude picture of each other or a video of your sexual activity you are committing the criminal offence of possession of child pornography and if you post it on social media or text it to each other you’re committing the more serious offence of publishing child pornography, even if it’s a selfie!