In one word using someone else’s computer over network 🙂 , Yes you heard me right Instead of maintaining physical server , Dedicated internet line etc.. we are renting someone’s computer over network.
Cloud is mainly divided into three main parts.
1)Infrastructure as a Service (IAAS)
2)Platform as a Service (PAAS)
3)Software as a Service (SAAS)
Infrastructure as a Service (IAAS)
If we want to rent only hardware like RAM,Processor, Hard disk , GPU etc.. then we will called it IAAS
Platform as a Service (PAAS)
If we want to rent a hardware along with Operating System like Linux , Windows then we will called it PAAS
Software as a Service(SAAS)
If we want to use any software/application which is already defined by someone in the cloud then we will called it SAAS. eg:Salesforce,RightNow,Workday etc…
May be below images will help you understand better
On premise vs Cloud
On premise ? Its simple using our own computer 🙂 which means everything is under our control
Refer the below image for more clarification difference Source fundamentalcloud
source link Boxes with blue color will be in our control and boxes with green color will be with cloud providers control.