There are two mode of github.Public and Private.You can put your repository into github and make it private for the team.Github has been improved a lot recently.
Code review comments can be made showing the change required.Difference with Pull request is helpful.
Issues: Informative tags can be added according to the issue,navigation is quite easy.Review process is less painful.
Tags/branch selection: Selecting branches from dropdown is easy to understand.Showing recent commits are helpful.
Gist: Code snippets can created easily to be shared
Commit graph: Github shows the density of commits done by user per month and creates a graph.It creates a lot of excitement among users.
Exploring interesting open source project expands a whole new level.
Major projects like linux, node, visual studio code are all hosted on github.
Followers system creates an engagement among open source enthusiasts.
Changing branches/tags while creating PR reloads the window,which is annoying.
Private repositories are paid comparing it with bitbucket which gives private and public repository option for free.
Recently github was acquired by Microsoft.A company famous for holding proprietary softwares now holds github creates a big threat to open source community called GitHub.For that reason many projects are shifting to alternative such as Gitlab because of trust issues.
Version control system is easy with git and github.The main power comes in when the project is open source and there are people who improve code quality,feature enhacement,fixes by creating a Pull request.