There are two HA/DR technologies that you can use. Official names are:
They are quite different but both rely on WSFC (except for Basic Availability Groups).
For FCI you need a shared storage which is also a single point of failure. You only have one copy of data and if it fails then everything fails. Also only one of the SQL Servers can run at a time, the secondary will be shutdown and cannot be used at all until fail-over happens. On the positive side, FCI takes care of all the databases including system databases (master, msdb), so you don't have to worry about logins, jobs etc.
AG doesn't need a shared storage. Each SQL Server instance has it's own copy of the database(s). All of the instances are constantly running with one instance in read-write mode and the rest are read-only.
But AG only replicate user databases so you have to take care of all the server level objects yourself (jobs, logins etc.).
Logins must have the same SIDs on all the servers!
Each time you add a new database you have to manually add it to AG group.
So depending on what HA/DR solution you want to use:
- For AG you need to install "stand-alone installation or add..."
- For FCI "new sql server failover cluster installation" and also "add
cluster node" on another server(s)
- It's also possible to configure AG on top of FCI but it only make sense if you have at least 3 servers and it's not commonly used. For example you can install FCI SQL1 on NodeA and NodeB, another FCI SQL2 in remote datacenter on NodeC and NodeD and then configure an async AG between SQL1 and SQL2 instances. In this case your HA is implemented using FCI and DR as AG.