1. To secure your user’s data from intruders
Like if a user enters the password “Kailash” this will be encrypted in the form of ciphertext like “sdfbsdfasdgvew”
2. Authenticate a domain.
when you try to grab an SSL certificate for your website you will have to authenticate that this domain is owned by you.
3. PCI compliance(set of rules to do online business)
If you are doing online business then you need to make sure that your website is PCI compliance.