In Salesforce1 the icon opens the navigation bar. Here you can go to many different places on Salesforce. Most often you’ll go to objects.
To customise the navigation menu, go to Setup -> Salesforce1 Navigation. Next, add the items you wish to the “selected” box. They’ll retain their order and the top one will be the landing page when opening Salesforce1.
Compact layouts are a convenient tool for showing key fields of an object at the top of the detail page. This is so they can be seen at a glance and is very convenient for Salesforce1, where people may be walking around, the screen is smaller et cetera. Compact layouts are similar to page layouts but they can only have up to 10 fields.
To create a compact layout, go to an object’s management settings and click “compact layouts”.
Simply name the compact layout and add the fields you wish to include (keeping in mind that the order will be retained). Click save.
Once the compact layout has been created you’ll need to assign it. Click compact layout assignments. Select the compact layout you wish to use and set it as the primary one for that object.
-Based on Salesforce Trailheads-