Setting wait condition in Selenium IDE or webdriver means pausing your test case execution till expected wait condition match with actual wait condition. You can view different wait condition examples for selenium IDE in THIS LINK and for web driver on THIS LINK. Selenium IDE has 2 related waiting commands towait till element's visibility or invisibility from the page. Those commands are "waitForVisible" and "waitForNotVisible" Commands. As you know, element's edit ability is different then element's visibility so don't be confused in these two terms.
This command will wait till element visible on the page. Once command will visible on page, selenium IDE will go for executing next command.
Same way, "waitForNotVisible" command will wait for invisibility of the element from page. Run bellow given example in your selenium IDE and watch what happens.
|type||//input[@id='text3']||Hidden Text box is visible now|
|type||//input[@id='text3']||To Hide text box is not visible now|