The current code states:
The Criminal Code does not now criminalize consensual sexual activity with or between persons 14 or over, unless it takes place in a relationship of trust or dependency, in which case sexual activity with persons over 14 but under 18 can constitute an offence, notwithstanding their consent. Even consensual activity with those under 14 but over 12 may not be an offence if the accused is under 16 and less than two years older than the complainant. The exception, of course, is anal intercourse, to which unmarried persons under 18 cannot legally consent, although both the Ontario Court of Appeal(3) and the Quebec Court of Appeal(4) have struck down the relevant section of the Criminal Code.

What does this mean in plain english
ex. if an 18 year old and a 15 year old had sex.