Why is 5y, 5 year forward rate used as a gauge of expected infation?

CFA General
#1

Can someone tell why is this 5y,5y used as a gauge of expected inflation?

https://fred.stlouisfed.org/graph/?g=caoT

Why not use 4y,4y or other combination for example?

#2

Also,

Why other analyts use the 10 year Breakeven Inflation Rate ?

When should we use each one?