ruby on rails - the difference between web app and web service -

suppose want build web service/app manage pms (property management system). contains 2 resources: room, , guest. can * add/remove/edit room * add/remove/edit guest * assign guest room 1) can design , implement in ruby on rails, web app? 2) can design , implement in ruby on rails web services? , please describe how plan use rspec test it.

i not know difference between web app , web service. can tell me why?

this web app mobile app native app , addmin panel communicate database service web used remote(this central database) ,suppose have server , hosting web services file 1-> have need create web services methods (insert update delete query) 2->via server url web services methods can call 3->you can or post method