Twilio Lookup is a phonebook REST API that allows developers to check whether a number exists, determine if it can receive text messages, and retrieve carrier data associated with a number. To validate phone numbers using the Twilio Node module, you need to install the Twilio module, set up your account SID and Auth Token, and create a file named lookup.js with a code sample that performs a basic phone number lookup. The basic functionality is free, but carrier lookups require an extra parameter and cost $0.005 per request. You can use this API to determine if a phone number is valid by trying to do a carrier lookup and checking for errors. Twilio Lookup also supports looking up invalid phone numbers and retrieving information from 3rd party data sources via the Twilio Marketplace.