As Salesforce indicates (https://developer.salesforce.com/page/Connected_Apps) a "Connected App" is an application that can connect to salesforce.com over Identity and Data APIs.
Connected Apps use the standard OAuth 2.0 protocol to authenticate, provide Single Sign-On, and acquire access tokens for use with Salesforce APIs. Connected Apps are designed to replace Remote Apps, which are now obsolete.
Quality Clouds uses a connected app to obtain an OAuth token to access your Org via the REST and Metadata APIs. If you already have a Connected App which you use for integration with external systems, and which meets the access level requirements described in the "Configuration" section below, it is not necessary to create a new connected app specifically for Quality Clouds.
Connected Apps add additional levels of control, allowing administrators explicit control over who can use the application, and various security policies to be enforced by the application.
This page describes how to set up a Connected App on your Salesforce Org for use with Quality Clouds.
Look for Connected Apps in your development environment by going to Setup > Apps > App Manager and click on New Connected App (marked in red)
In Salesforce Classic, from Setup, enter Apps in the Quick Find box, then select Build > Create > Apps. Under Connected Apps, click New.
This will present a screen similar to that shown in the following figure:
Fill out only following fields and leave the rest blank:
Connected App Name
+44 20 3290 0456
QualityClouds connection for REST API calls
Check Enable OAuth Settings.
Set the Callback URL to: https://scan.qualityclouds.com/sf_instance/code_callback
In Available OAuth Scopes, select "Access and manage your data (api)", and "Perform requests on you behalf at any time (refresh_token, offline_access)".
Click Add. These settings allow Quality Clouds to access the logged-in user’s account using APIs, such as REST API and Bulk API. They also allow Quality Clouds to refresh the token if it has expired, up to the expiration date of the refresh token itself, which can be configured on the Connected App.
Click Save and Continue
Click App Manager again. Locate your newly created QualityClouds and click the dropdown arrow on the far right.
Note the Consumer Key and the Consumer Secret values (click the Click to reveal button to see the secret key).