Azure App Service is fully-managed cloud platform. It is platform as as service. (PaaS)
Keys features are:
- Quickly build, deploy, and scale enterprise-grade web, mobile, and API apps running on any platform.
- Link with source controls, TFS (via Visual Studio), FTP, FTPS, WebMatrix, CodePlex, GitHub, Dropbox, Bitbucket, Mercurial and local Git
- Meet rigorous performance, scalability, security and compliance requirements
- Fully-managed platform to perform infrastructure maintenance.
- Supported languages,.NET, node.js, PHP, Python and Java
Link to Azure App service plans capabilities and limits.
For BASIC, STANDARD, PREMIUM and ISOLATED plan, you can deploy to unlimited app (website).