help about loop and multitask

hello,
i love arduino it's so easy to me but i need some help to understand some information

i know this is the default for any sketch

void setup() {
// put your setup code here, to run once:

}

void loop() {
// put your main code here, to run repeatedly:

}

i understand that loop will run repeately,

i need help in next

void setup() {
// put your setup code here, to run once:

}

void loop() {
// put your main code here, to run repeatedly:
function1

delay(100);

function2

}

void function1(){
has a loop and delay(100)
}

void function2(){
has a loop and delay(100)

}

my question is in the loop there are two function each one has a loop and delays, now if i start this sketch the both function1, function2 will run in same time or each one will wait until he other finsh delay and it's loops ?

and how to make multitasks ?
i have read in some blog there are arduion os any one have any information about this?

i am sorry for bad english

thank you

There is no default multitasking.
One function will run, blocking all the time it spends in "delay", then he other will run.

Look at the blink without delay example for ideas if you need things to seem to happen simultaneously.

thank you mr AWOL i will try to understand it thanks