Announcements keep everyone in your company informed regarding updated information about various topics in SharePoint.  The announcement web part is usually included in every template starting out and is one of the easiest web parts to maintain.

Once you have set up an Announcement web part of your site, you can start adding new announcements.  To add a new announcement click Add New Announcement on the bottom of the Announcement web part.
 
Now you will be able to enter in specific information.  Give your announcement a title and describe what the announcement is about in the body.  The first feature to pay attention to is that you are able to attach files to your announcements.  For example, if you created an agenda in a Word document for the meeting you could attach it to the announcement for everyone to download ahead of time.  Secondly, you can set and expiration date.  This will help you maintain that the most current announcements are visible at all times.  No one cares about an announcement for a meeting last month.
 

If you are forgetful like me, you can also choose to be alerted about Announcements as well.  To set up an alert, click on the title of the announcement you want to be alerted about.  On the next screen, click Alert Me.
 
You will then be taken to the Alert criteria screen.  For more information regarding setting up alerts, check out a previous blog I have written on the topic.
Overall, Announcements are a fast, simple method to keep your employees informed every time they log into SharePoint.