You may find the Fastpass+ section on the Disney website to be helpful.
Learn about Disney FastPass+ service and how it works at Walt Disney World Resort in Florida.
disneyworld.disney.go.com
Tier 1 does not mean there is no standby line.
In Epcot, Hollywood Studios, and Animal Kingdom there are tier 1 and tier 2 FP+ selections.
The absolute headliners are tier 1 and the rest are tier 2.
You select 1 tier 1 and 2 tier 2 to book ahead of time if you'd like.
After you use them you can book another of either tier one at a time.
Use and repeat.
In Magic Kingdom there are enough attractions overall that the tiers are not needed.
Feel free to stand in the regular standby line for any of the attractions.
Its somewhat similar to other amusement parks that have a special pass you purchase at a hefty price to "skip the lines". That does not mean there is not a regular line for those rides.
Nice thing about Disney World is for now its at no additional fee and you can pre book 3 per each day on your ticket.