i can understand the ability to make a brainwallet with electrum and iits remembering the 12 words seed but kinda sucks because words are made by the wallet and your self .
i see a lot of people speaking about brain wallet , basically if i want to make one how i will do that exactly ?? if i have wallets like bitcoin core , multibit etc ... ? pretty sure it's all about remembering the passphrase but those haven't unless you mean the password that helps you to send coins
i see a lot of people speaking about brain wallet , basically if i want to make one how i will do that exactly ?? if i have wallets like bitcoin core , multibit etc ... ? pretty sure it's all about remembering the passphrase but those haven't unless you mean the password that helps you to send coins
Memorize anything you want to use as a brainwallet, convert it in a repeatable way to a number that would serve as a private key (between 0x1 and 0xFFFF FFFF FFFF FFFF FFFF FFFF FFFF FFFE BAAE DCE6 AF48 A03B BFD2 5E8C D036 4140)[1] and calculate the address[2]. Done.
The problem is that humans are very bad at picking random things. We think when we smash our face at the keyboard is random, but its actually pretty predictable what will happen. Thus a brainwallet based on electrum is actually a better way than to do it yourself. If you want some ideas how to create a brainwallet with sufficient entropy I suggest this[3] thread.
[1] https://en.bitcoin.it/wiki/Private_key
[2] https://en.bitcoin.it/wiki/Technical_background_of_version_1_Bitcoin_addresses
[3] https://bitcointalk.org/index.php?topic=885616.0
say what , so basically the adress is generated from the random words ?
Well indirectly yes. A brainwallet is a way to memorize a larger number that represents your private key. The private key is tied to a certain address as the address is calculated from it.
same goes private keys ? are those actions reversible ?
No, they are not reversible. The private key has a corresponding public key. If you spend coins the public key gets known. It is to our current knowledge not possible to calculate a private key from a public key. You would have to brute force it and due to the larger numbers thats not possible either. If you never spend any coins the public key is not known and your private key is also protected by the hash functions used, which are also not reversible. Hash functions are also considered to be quantum secure.
means someone with the pass can guess adress , and someone with adress can get your password ( which sucks) ? 
If anyone should guess your passphrase and the way you convert it to a number they have your private key and can spend your funds. Thats why its so important to use something random and not something like a quote from your favorite book. It is not possible to get the private key from your bitcoin address.
Brain wallet = human memory.
Think about something (easy to remember but hard to predict which has to be meaningless)
For instance: "alice gone to barber shop to drink coffee"
Then use this page; https://brainwallet.org/#generator (You can download it and use it offline, it's coded in JS so it works client side).
For our example our public address is: 19JKY4xxx8hveoXp6nucHPQ6ayu2EqtAVY and it's WIF priv key is: 5KF4m3tGeV5BfQFFmm7RUzmcgmAMA5WW23Bru22J98rSgfNrZFM
Ps: do not use known catchphrases like "to be or not to be" https://blockchain.info/address/1J3m4nneGFppRjx6qv92qyz7EsMVdLfr8R
Think about something (easy to remember but hard to predict which has to be meaningless)
For instance: "alice gone to barber shop to drink coffee"
Then use this page; https://brainwallet.org/#generator (You can download it and use it offline, it's coded in JS so it works client side).
For our example our public address is: 19JKY4xxx8hveoXp6nucHPQ6ayu2EqtAVY and it's WIF priv key is: 5KF4m3tGeV5BfQFFmm7RUzmcgmAMA5WW23Bru22J98rSgfNrZFM
Ps: do not use known catchphrases like "to be or not to be" https://blockchain.info/address/1J3m4nneGFppRjx6qv92qyz7EsMVdLfr8R
Or the famous "correct horse battery staple"[1] brainwallet -> https://blockchain.info/de/address/1JwSSubhmg6iPtRjtyqhUYYH7bZg3Lfy1T
[1] https://xkcd.com/936/