What it's all about!!
We dress differently when we go out with friends to how we would dress for an important interview. Similarly, we change the tone of language to suit the context - if we want to get the job!
Standard English is formally and grammatically correct English. It is the written equivalent of wearing a smart suit.
You are expected to use Standard English in all your English exams. This means not using slang, informal, or chatty language, and it means making sure such things as your verbs are in agreement.
Example no 1
Us as a young generation say "Kids"
Adults say "Children"
Example no 2
Us as a young generation say "Blokes"
Adults say "Men"
Example no 3
Us as a young generation say "We was going out to this caff"
Adults say "We were going to the cafe"
Example no 4
Us as a young generation say "There was two of us"
Adults say "There were two of us"
Example no 5
Us as a young generation sometimes say "She gave him a right earful"
Adults say "She told him off"
And so it goes on....
The only part of your English exam where you can use non-standard English is in their descriptive writing. But it pays to be cautious.
Only use non-standard forms when you are writing direct speech, That way, the examiner can see that you are consciously adadpting language to create specific effects.