Cat get in heat for the first time, it gets between 5 to 11 months.
Since home cats live all their life's under artificial lighting, her heat will be in all season of the year and last in average for 7 days.
With the start of the heat the cat start to change her behavior, she will show since of self-indulging that include rolling on the floor and rubbing her body on different objects, numerous and loud yowling – the purpose of this is actually a "message" to male cats that she is in heat. She will also lift her buttocks preparing for mating act and secreting hormonally smell to attract the male cats.

The mating act! 

A lot of male cats will react to the heat female cat and her smell in order to wine possibility to continue his generation.
They will fight on their share, usually these fights will and with only loud yowling but there
is a possibility that it will evolve to physical violent, and in the end to a real war.
The mating act last only a few seconds to minutes, the male climb on the female from behind and bite her nape, so she will not move. This bite release material like morphine
to the female blood cycle, which induce pleasant feeling on the female and even lessen
her pain.

Unlike in human and other animals, the ovulation in cats is different, if the ovum is not fertilized it doesn't die, the mature ovum stays in the ovary. When the cats mate, the male cat penis makes stimulation in the female vagina, which releases the ovum.
This is the reason why there can be a situation part of the kittens are from another father.
Usually after the mating the female will attack the male that is because the removal of the male penis is painful for the female.

Here are the signs that according to them you will know if your cat is pregnant! 

Physicals signs:

She is no longer in heat.

Here nipples are turn pinker and a little more swollen.

She has increased appetite.

She is vomiting.

In the 5 week you will see her belly getting bigger.

The change in her personality:

She will be friendlier and look for affection.
In the late stages she will start looking for a quite comfortable and cozy place far away
from everyone eye.

Cat pregnancy last between 60 to 67 days, the average is 63 days.

Feeding during the pregnancy:                        

During the pregnancy you should feed her with kitten's food, she will keep on eating
kitten food until she stops breast feeding them.