Let's Encrypt vs Azure Security Center: What are the differences?

What is Let's Encrypt? A free, automated, and open Certificate Authority (CA). It is a free, automated, and open certificate authority brought to you by the non-profit Internet Security Research Group (ISRG).

What is Azure Security Center? Gain unmatched hybrid security management and threat protection. It is a unified infrastructure security management system that strengthens the security posture of your data centers, and provides advanced threat protection across your hybrid workloads in the cloud - whether they're in Azure or not - as well as on premises.

Let's Encrypt can be classified as a tool in the "Certificate Authority" category, while Azure Security Center is grouped under "Security".