What is the difference between formal and informal writing in English? See below:)

FCE WRITING PART 1 PREPARATION

FORMAL and INFORMAL WRITING EXERCISE

by Bob Wilson at autoenglish.org

HOME FCE WRITING FCE READING FCE USE OF ENGLISH CONFUSING WORDS WRITING EXERCISES OFFICIAL SITE
 APOLOGISING
FORMAL INFORMAL
I would just like to apologise for forgetting your birthday. I'm really sorry I forgot your birthday.
 EXPLAINING
FORMAL INFORMAL
The first step would be to What you need to do is...
 EXPRESSING ENTHUSIASM
FORMAL INFORMAL
I would just like to say I think that is excellent news. I think that's fantastic news!
 EXPRESSING PREFERENCES
FORMAL INFORMAL
I would rather visit... I'd really prefer to visit...
 REQUESTING INFORMATION
FORMAL INFORMAL
I would really appreciate it if you could forward the train times to me. Can you send me the train times?
 THANKING
FORMAL INFORMAL
I just want to express my sincere thanks for all you have done. Thanks a lot for everything you did for us.
 SUGGESTING
FORMAL INFORMAL
I recommend going to a Spanish restaurant. You really must go to a Spanish restaurant.
Formal and Informal English