As far as I know, all bitcoin addresses start with a "1" or "3" prefix. I've just started using electrum wallet and all the addresses it generated had a prefix of "b", or even "bc". Is this legit or some scam, and if legit, does it have a special meaning (like segwit addresses starting with "3" prefix) and where can I read more about it?
These are native SegWit addresses, specified in BIP173 using a format called Bech32. They begin with 'bc1'.
Addresses that begin with a 3 are P2SH addresses, an address format that has been around for over 5 years now. They were originally used by multisig wallets like CoPay and GreenAddress, which only saw limited usage. However, SegWit can also be used in compatibility mode, using the existing P2SH format, so that old clients can send to it. This gave rise to the myth that '3' addresses are specifically for SegWit.