In the context of a company, the memorandum or memorandum is a short text that is used as a means of communication within it. The information that is usually transmitted through it, among others, is usually a warning to stop doing certain types of activities, a change in responsibilities or a reminder to attend a meeting.
Here is an example:
Irun, April 5, 2017
To: Jose Ramón Antunez
From: Human Resources Department
We have been noticing in recent months that you arrive at your job later than the time that was set for your incorporation to work. We remind you that the repeated lack of punctuality when starting to work is punished in this company with a financial fine and, even, with dismissal. We therefore want to recommend that you go back to work at the established time. We also want to remind you that the human resources department is at your disposal to deal with any problem that has to do with your work.
Ángel Gameto Goles
A memorandum outside the context of a company can be a booklet where the things to be remembered are noted or a text that states something that must be taken into account to make a decision or deal with a matter or a diplomatic communication where facts and reasons to be taken into account when dealing with a serious event.