Web Apps, APIs and Services

Applications deployed on web servers accessed via web browser and coded in a browser supported language (html/css/js)
Deployment advantages: web browser ubiquity convenience standards distribution no installs (almost)
Development advantages: web standards tools frameworks
Web app vs RIAs vs Desktop app
Client-side Technologies: HTML/CSS/JS/AJAX Dojo
Server-side Technologies: Java Servlets/JSP PHP .NET/ASP Groovy/Grails Ruby/Rails Python/Django Comet(Push AJAX)
Web App Servers: Glassfish Tomcat Jetty
Tools: Netbeans Eclipse Firefox/Firebug

Set of routines data structures object classes and/or protocols provided by libraries and/or operating system services in order to support the building of applications
Can be a web app that exposes its business logic as a set of routines using a development library for the required classes
Web APIs are just Web Sites - Paul Downey
All the Web APIs for your needs: Programmable Web!

Software system designed to support interoperable machine-to-machine interaction over a network
Compared to web apps which support user-to-service interaction web services promote service-to-service interaction by using well-defined interfaces
Web services are frequently just Web APIs...
SOAP/WSDL vs REST web services
Technologies: JAX-WS/Metro and JAX-RS/Jersey
Twilio SMS gateway API access is available by request.

Open Lab Tutorials:

REST

SOAP