If load balancing is spreading your users over more servers, that's not possible with MSSQL (Buy Oracle RAC in that case, but you'll have to win the lottery first 😉 )

About failover: MSSQL uses the shared-nothing principle, which means 1 server is active, the other server is passive, doing nothing until the active server crashes (some variants are possible, but that's beyond this answer).

About Mirroring: You can't use that database until the original database crashes.

Make sure you know both pros and cons of these concepts; this site is a good start.