The best way to use Zoho CRM is to learn it -
http://www.zoho.com/crm/[
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API Key (there is only one) is your key to access the online API - you will get your own when registering to Zoho CRM...
Authentication Token (can be more than one) used to connect the current API call to one of you Zoho CRM credentials. As you can access the same API from different applications you may want to assign different credentials to each of them...