This sentence means that they have told you a benefit to something. For example, let's say that you are at a job interview, and they tell you that you get paid vacation time off. They would say "That's the perk of working with this company," meaning that your paid vacation is a benefit to you being employed with them. Another example could be you asking your friend why it is important to learn another language. Your friend could say "Learning another language helps you make global friends, and that's a great perk." The great benefit, or perk, of you learning English (in this example) is that you can make friends who speak English, aside from your native language. Hope that makes sense!

Perks are special benefits that are given to people who have a particular job or belong to a particular group. e.g. Not having to get up early is just one of the perks of being retired.