Links can conceal information by making a user click on a word such as "enter here." This is concealing information because in order to access what you are trying to get to, you have to go through that particular link. A link can be used either to make things more organized on a page or to hide content that a user may or may not want to see. The reason this is an example of how links reveal information is because when a user clicks on a particular link, a new page of information is then revealed.
This is my example of a link that reveals and conceals "cla clik." Without actually clicking on my link, you will have no clue where it leads you. This is concealing information from you. If you do decide to click on it and enter into the unknown it will reveal a new page of information. Another example is once you enter the link I provided, you have another choice of whether to enter the links on the next page. Those links also hide and provide information to users. Whether you decide to let the links reveal information to you or keep it concealed is up to you.