Hi manesh80,
Reference letter and work experience letter would be same thing - It is on the company's letter head, with official address, phone numbers, fax, email, website add if any, duly signed and stamped by the HR or director. It's first paragraph should describe when you joined, your last salary scale, number of hrs you work per week, full or part time, date you left or are still working, your job title etc. The main body should mention what you mainly did in bullets points i.e main duties performed as per NOC.
That would be all. You can also submit your employment contract which you signed when you joined the company - there also it describes your duties, working hours etc.
Hope that will help.
Cheers
K