Life should NOT be a trip to the grave with the intention of arriving safely in an cool and well preserved body, but rather to skid in, chocolate in one hand, beer in the other, body wrecked, totally worn out and screaming WOO HOO what a ride!
Are you just starting out somewhere Sattaruvu? You've put up about 3 or 4 basic question posts, if terms are confusing to you at your work then you should be checking with them on what the terms mean in your company, or become familiar with Google or the local Search utilities here.
Learning how to find information makes you a better Tester.
In a real life, there are few requirements which are so obvious that most often they are not listed as the testable item. For example, systems shouldn’t crash, the backgruond color and the foreground color must not be the same, text should fit in the buttons etc etc. These are known as implied requirements which are written in rare cases but very critically important. As a consequnces for this, most of the times we do not create test cases for them, as it’s obvious when they’re tested.
Implied requirements are problematic . They are the promises that are "assumed " in the mind of the person requiring the product or the service. They are expectations or the requirements that the person assume, will be there and hence does not see the need of stating them.
if acustomer says that he wants margin of 3
here the customer assumes that margin is in % so it is not stated in the reqirements document as 3%. this is the implied requirement. it becomes problematic if the develoer or the tester do not know that margin is in % as it is not stated.