Starting with “3” is a P2SH Nested Segwit addresses.
No,
Addressed starting with 3 is P2SH, but it's not always a segwit address.
Look at the bold part of achow101 post
So ive always had my bitcoin in my hardware wallet. Now there are 2 options: Legacy and Segwit. Whats the actual difference ?
Legacy means that you will be using addresses of the form 1... Segwit means that you will be using addresses of the form 3... or bc1... (one is for P2SH nested segwit and the other is for native segwit).
Note that 3... addresses are for P2SH addresses in general and are not just for segwit. bc1... addresses are for segwit specifically but not all wallets support it yet.
And following post made by o_e_l_e_o
Based on your previous comment there seems to be conflicting information as I have the dreaded 3 to indicate that it is not multi-segwit.
Addresses which begin with 3 may or may not be SegWit, and may or may not be multi-sig. It all depends on how you set it up. Electrum does not create SegWit addresses beginning with 3 though - it will only let you import them. So if you created your 3 addresses in Electrum, which it very much sounds like you did, then it will be multi-sig legacy rather than SegWit or multi-sig SegWit.