Former refers to the first thing that will be mentioned when there are two things that need to be referred to. Latter will refer to the second thing when there are two things that need to be referred to.
For example, the sentence may be this: Tricia and Cyriel have decided to become open about their relationship. If you asked who is the former between Tricia and Cyriel, it would be Tricia because this is the person that is mentioned first while the latter will be Cyriel because this is the second name that is mentioned in the sentence. Take note that former and latter are normally used for other items too.