Macbook air boot time
There are a number of benefits to flash memory over HDD:


No moving parts
No spin up time
No electric motor using your battery charge
"Seek Time" isn't really a thing, since there's no drive head moving to read a different sector of HDD platter


During boot, your computer reads a lot of software from your boot volume into memory. The time it takes to do this is drastically reduced when using a SSD (flash) instead of an HDD.