How to connect to an EC2 instance?
There are 4 native ways to connect to Linux EC2 instances and 3 native ways to connect to macOS and Windows EC2 instances. Some of them are SSH based (Linux, macOS), RDP based (Windows, macOS) and others just may feel and look like if SSH or RDP protocols were used. They all provide a remote interactive access to an EC2 instance and some even more than that.
EC2 SSH client (Linux, macOS)
A SSH client can be considered as a default way to connect to Linux and macOS EC2 instances. AWS recommends to create (or attach) a pair of .pem or .ppk keys when you initiate new instances.
The SSH connections for EC2 instances are encrypted and fairly secure. Way less secure are your keys. Those can be destroyed, lost or intercepted from the local machine unexpectedly easily.
EC2 RDP client (Windows, macOS)
A RDP (Remote Desktop Protocol) client can be seen as a default way to connect to Windows and macOS EC2 instances . Similar pros and cons as for the EC2 SSH client solution.
EC2 Instance Connect (Linux)
EC2 Instance Connect is a must have for Linux Amazon and Ubuntu instances. SSH based but much more convenient and secure than using EC2 SSH client. Learn how to set up EC2 instance connect.
EC2 Session Manager (Linux, Windows, macOS)
A not SSH based solution being part of a larger service - Systems Manager but can be used independently of it. Available for all Operating Systems (except for some specific Windows Server instances) gives more features than EC2 SSH or EC2 RDP clients.
EC2 Serial Console (Linux, Windows)
Available for all Operating Systems but not for all instance types and regions. Optionally can be SSH based. Has a big advantage over the other solutions - can be active when booting and closing EC2 instances.