FYI is the abbreviation for the English language term "For your information”, which in Portuguese means “for your information”.
Its use is very common in email messages when the sender wants to make known something new that may be of interest to the recipient. In this case, in the subject or in the message body there is only FYI, indicating that the attached information does not necessarily require a reply, that is, it is just an informative message.
In Portuguese, the equivalent terms would be PSC which means "for your knowledge" or PSI "for your information".
When the letter J is added at the beginning of the acronym, abbreviating the word just which means "only" or "only", the term becomes "Just for your information” (JFYI) which is literally “just for your information”. It is also common to use the expression “For your information only” which has the same meaning. In both cases, it reinforces that the message is informational only.
Another abbreviation commonly used in emails is FYG, which stands for
For Your Guidance, which means "for your guidance". It is a more technical abbreviation, often used in the context of business administration, which is often used in the subject or title of the email, to indicate that the email contains instructions that must be followed by the person who received the email.When a response from the recipient is required, the term used is FYA which means "for your attention” indicating that that message requires a response from the receiver.