What is it?
Recently, internet explorer has had a critical security vulnerability discovered which basically can allow a hacker to remotely mess with your computer with the same rights as a user that viewed a specially crafted webpage using an internet explorer version that is vulnerable.
What does this mean?
A hacker can do anything on the computer that the current user can do (therefore non-administrator user would be less impacted). For example, delete files (if the user is an administrator, the hacker could delete all files on the computer), delete photos, load infected websites, remove anti-virus software (if the user is an administrator) etc. This is why it is crucial that you do something about it!
What can I do about it?
If you have automatic updates enabled in internet explorer: carry on as normal. Internet explorer will have automatically updated itself. If you install all your updates manually, update as fast as you can! If you do not know how to do this, or want to check if you are protected, open internet explorer, click on the cog in the right hand corner and then click on ‘about internet explorer’. Then make sure that automatic updates is enabled and that your internet explorer is on the latest version (at time of writing for internet explorer 11 it is 11.0.9600.17105)
For more information visit https://technet.microsoft.com/library/security/ms14-021