when does a toddler become a pre-schooler?

[Phteven]

There is an aspect of Yasin's development that has been bugging me so today I've been googling a bit and looking around lots of websites.
I've been finding that lots of the toddler information seems to be about younger children and the pre-school information seems to be about older children.
So now I'm just curious about when a toddler becomes a pre-schooler.

[widdly]

This is how i thought it went

0-1 baby
1-3 toddler
3-5 preschooler

Thats what it says in some of the books i have read any way, probably there are a lot of different ideas out there.