Global Actions

Lightning App

This used to be called Create, now after Spring '18 it's Global Actions.

Salesforce Mobile

Lightning for Outlook or Lightning for Gmail

Note you can only use Global Actions in LFO LFG

Salesforce Communities

See Setting up Knowledge on Communities for a step by step guide on how to set this up.

Quick Actions

Record Actions

These are standard, and not customisable (yet). 

Standard and Custom Actions on a Lightning Page

Actions on the standard Chatter Object

On a Home Page Component

Salesforce Mobile App

A Related Record Component on the Lightning Page

Mass Edit on List Views

As at Spring '18 only on Cases, Leads and Custom Objects.