When you login to leaf, you will see your ancestor chart:

Each of your four ancestral lines is given a different color. Light colors:

mean that an ancestor still has some work that is needed -- perhaps a missing birth date or missing LDS ordinances. Dark colors:

mean that the ancestor is "complete".

If you hover over an ancestor, then that person's name is shown in a floating box:

If you click on an ancestor, then the box shows the basic information and what is missing for that person:

If you click any of the menu items shown at the top of the page or on a person's menu, then you can show an ancestor chart, a profile page, a descendant chart, or a search page for that person. For example, clicking on a person:

and then clicking on their Ancestors menu shows an ancestor chart with that person at the center:

To customize how leaf searches for missing information, you can click on the button. See the Settings Help for more information.