This is a platform where people sell and buy Software(Android, PC, iOS), Websites and Domain.They are trusted, their reputation is in industry just like Freelancer.com.
If you created any site and you want to sell it then Flippa is best for you, you can sell your site here by adding some price to your site, or you are developer then you can sell your created app in flippa without any fee, mainly flippa will take when your item will sold, it will take some% of it not much just little.You can also sell or buy domain here in cheap rate.
If you want to buy site/apps/domain then that site provide good product also because people are create website/apps with full of their limit so you will get good result.You can also hire developer for creating a website according to you.
So in both way this site is good for daily life and as well as professional use.