Appengine is a service provided by Google. Using Appengine we can use the Google cloud to run our web application. Google cloud is one of the heaviest controller of internet traffic. They provide a perfect load sharing technique. The appengine is free of cost upto a certain Mb. It cost very less for higher Gbs.
Appengine provide a development SDK . It is a miniature form of the original appengine. We can develop our application in the SDK and upload the application after the perfect evaluation. Appegine provide a web server. When we use the appengine our application becomes a part of the the web server and works along with it. It also provide a object database which is quite different from relational database. We use a query language called GQL, similar to our normal query language.
Appengine SDK provide a small database machine along with it. The database machine is also a miniature form of the original database engine provided by appengine. The object database provide all the features of the relational database we know.
The appengine SDK run the the server in the IP 127.0.0.1 that is the localhost IP address. The port used as default is 8080. the originally used port for Internet is 80. 8080 is used to look similar to the original. We can change the port number also.