What are the features of Schedulable class in Salesforce?

The Apex Scheduler lets you delay execution so that you can run Apex classes at a specified time. This is ideal for daily or weekly maintenance tasks using Batch Apex. To take advantage of the scheduler, write an Apex class that implements the Schedulable interface, and then schedule it for execution on a specific schedule.
You can only have 100 scheduled Apex jobs at one time and there are maximum number of scheduled Apex executions per a 24-hour period. See Execution Governors and Limits in the Resources section for details.
Use extreme care if you’re planning to schedule a class from a trigger. You must be able to guarantee that the trigger won’t add more scheduled jobs than the limit.
Synchronous Web service callouts are not supported from scheduled Apex. To be able to make callouts, make an asynchronous callout by placing the callout in a method annotated with @future(callout=true) and call this method from scheduled Apex. However, if your scheduled Apex executes a batch job, callouts are supported from the batch class.