I tried to use Jmeter but I was not clear about the use of timer in Jmeter
Can any one please let me know how timer is useful for load testing Jmeter and where it is beneficial?
Jmeter, by default doesn't add any waiting/pausing time between two or more consecutive requests.
Now imagine that you sent a thousand requests to the web server under test in matter of seconds. What will this do?
This will cause an overload and Jmeter will overwhelm your test server by making too many requests in a short span of time.
To overcome this, we have the concept of timers in Jmeter. Timers allow JMeter to delay between each request which a thread makes. When you add more than one timer to a Thread Group, JMeter keeps the amount of the timers and pauses for that amount of time before executing the samplers to which the timers apply.
Jmeter official documentation has an excellent read on this.
Also, you can have a detailed read of the timers in this tutorial by Blazemeter.
Another helpful link would be this.
Last but not the least, please explore more using Google. There are a lot of resources on timers.