AppExchnage is one of the strongest strengths of Salesforce CRM. Early on, Salesforce understood that there is power in numbers. They encouraged partners to create applications to be built for Salesforce CRM that could be used to enhance the customer engagement experience. So… they introduced the Salesforce marketplace an AppExchange portal. The AppExchange is a business app store with over 3000 apps (some are free and some paid), which includes Salesforce integrations with MailChimp, Xero, Quickbooks, DocuSign, AdobeSign, etc. There are more and more integrations and solutions added every day and this is why Salesforce is the undisputed leader in the CRM space.
https://getoncrm.com/how-salesforce-mobile-app-can-be-beneficial-for-your-organization/