So let's say I have a list of 100 emails, and I want to send one text to all of them but I don't want them to know that I've sent the same thing to other people, I want them to think its only for them.
How can I do such thing via my Gmail?
It IS NOT SPAM.

Use the "bcc:" feature.

Thanks for the answer, but when I use bcc I still get the full list of all the recipients!

BCC is BLIND carbo copy, vs CC which is Carbon copy... BCC should not reveal that.. they are different fields. Are you sure you aren't confusing the two?



In e-mail terminology, Cc stands for "carbon copy" and Bcc stands for "Blind carbon copy". The difference between Cc and Bcc is that carbon copy (CC) recipients are visible to all other recipients whereas those who are BCCed are not visible to anyone.
To specify the recipients, an e-mail message can contain addresses in any of the 3 following fields:


To: field recipients are the audience of the message
CC: field recipients are others whom the author wishes to publicly inform of the message (carbon copy)
BCC: field recipients are those being discreetly or surreptitiously informed of the communication and cannot be seen by any of the other addressees.

It is common practice to use the BCC: field when addressing a very long list of recipients, or a list of recipients that should not (necessarily) know each other, e.g. in mailing lists.
Comparison chart



http://static.diffen.com/css/img/edit.png (http://www.diffen.com/difference/Special:EditTable?diffenVal1=Bcc&diffenVal2=Cc)
Bcc
Cc


Sight
-Receiver cannot see Bcc
-Receiver can see Cc


Replying
-Bcc's cannot see the receiver's reply
-Cc's cannot see the receiver's reply




Example of CC vs BCC

From: Frank Sinatra
To: Kurt Cobain
Cc: Bob Dylan; Jim Morrison
Bcc: Mark Knopfler; Paul McCartney
In the above example, all recipients of the email (including Mark Knopfler and Paul McCartney) will see the following email header information when they receive the email:
From: Frank Sinatra
To: Kurt Cobain
Cc: Bob Dylan; Jim Morrison

This means that none of the recipients will know who the Bcc recipients are. Each of the BCCed recipients will, of course, realize that they were on BCC but they will not know who else was on BCC



Shamelessly lifted from Bcc vs Cc - Difference and Comparison | Diffen (http://www.diffen.com/difference/Bcc_vs_Cc)

Thanks for such great and detailed info.
Positive, when I use bcc, and click on the details, everything is showed to me.

But perhaps that's because I use my own emails ?
I use 1 to send a test mail to 3 other mails.

Of course YOU see who you sent to, but the recipient only sees themselves. When I send such an e-mail I send the e-mail to myself and then BCC the rest of the recipients.