Google Nexus 5 - Touch; Touch and Hold; Phone Calls; Make Phone Calls

Phone Basics 8
Touch
When you want to type using the onscreen keyboard, select items onscreen such as application
and settings icons, or press onscreen buttons, simply touch them with your finger.
Touch and Hold
To open the available options for an item (for example, a contact or link in a Web page), touch
and hold the item.