REST stands for REpresntational State Transfer (REST).
SOAP Stands for Simple Object Access Protocol (SOAP).
Architecture style vs Protocol
REST is an architectural style.
SOAP is a protocol.
RESTful web service can return the response in various format e.g. JSON, XML and HTML
SOAP web service you tie your response with XML because actual response is bundled inside a SOAP message which is always in XML format.
Processing a RESTful web service request is much faster than processing a SOAP message because you need to less parsing. Because of this reason RESTful, web services are faster than SOAP web service.
REST requires less bandwidth and resource than SOAP.
SOAP requires more bandwidth and resource than REST.
RESTful web services utilize URL to identify the desired resources to be accessed.
SOAP uses XML messages to identify the desired web procedure or resource to be invoked.
Security in RESTful web service can be implemented using standard and traditional solutions for authorized access to certain web resources.
While to implement security in SOAP based web services you need additional infrastructure in the web to enable message or transport level security concerns.
JAX-RS is the java API for RESTful web services.
JAX-WS is the java API for SOAP web services.
In REST based web-services every entity is centered around resources.
while in the case of SOAP web service, every entity is centered around interfaces and messages.