Thanks.
And do i get it right, that i can create BTC wallets (in electrum or multibit for example) on completely OFFline computer? And the adress(es) i create would be functioning? Se even when i create the wallets (and thus BTC adresses) on completelly offline computers, i can sent there BTC, even though these adreesses have never seen/touch online computer...?
yes you generate the private keys with the wallet you install offline and only use the public key in form of the bitcoin address (starting with 1) to give others to pay you bitcoin.
The only situation i will have to use the private keys on internet connected computer is when i want to SENT some bitcoins from these offline created wallets? Correct?
no you don't use the private keys online, they will remain offline.
for spending bitcoin you need to make a transaction, that transaction can be made without the private keys and only be signed (to be come valid for spending) with the private keys.
in the link to the documents of electrum that was given above, it is explained more. but in short you make the transaction (unsigned) online and transfer that to your offline computer containing your private keys to sign it. and then transfer the signed transaction to online computer to send out (broadcast) to the network.
Or in other words, creating BTC wallet(s) (which are collection of BTC adresses (which are further a collection of private and public keys) right :-)?) and receiving BTCs to these wallets can be done completelly offline? Creating BTC wallets and receiving funds to them (from "outer world") can be done offline...?
yes since bitcoin is not a physical thing to have.
there are only transaction which are being kept on the blockchain and to spend them you need the key only.
The only situation i need a connection to the internet is:
1) Checking the current actual BTC balance on these wallets and
2) Sending BTCs from these wallets somewhere else
Correct?
your offline wallet will ALWAYS stay offline and you only transfer the transaction via a text file or in a safer way with QR codes that you scan.