If you type
monero-wallet-cli it will show you all available options for set with a bit of explanation for each of them and their options. That is:
set Available options:
seed language - set wallet seed language;
This is the language of your 25 word mnemonic seed. The default language is English as far as I know and also what most people choose.
always-confirm-transfers <1|0> - whether to confirm unsplit txes;
If this is set to 1 if will ask for confirmation before sending the transaction. If set to 0 it will not.
store-tx-info <1|0> - whether to store outgoing tx info (destination address, payment ID, tx secret key) for future reference;
If this is set to 1 it will store outgoing transaction info. Note that the tx secret key is quite important to save, since it is able to prove that you paid someone in case of a dispute. Bitsquare also requires the secret tx key in case of dispute
default-mixin <n> - set default mixin (default default is 4);
This is fairly straightforward.
auto-refresh <1|0> - whether to automatically sync new blocks from the daemon;
If this is set to one the wallet will refresh automatically when it is connected to your own daemon or a remote daemon. Note that the daemon is
monerod. If this is set to 0 you'll have to type
refresh once in a while to get new blocks.
refresh-type <full|optimize-coinbase|no-coinbase|default> - set wallet refresh behaviour;
I am not entirely sure about this one, but I think if it is set to
no-coinbase it won't scan coinbase transactions for outputs / transactions that belong to your wallet. Conversely,
optimize-coinbase will look if the first output of the coinbase transaction belongs to your wallet and if not it will skip it. I'd advise to not change this unless you know what you are doing.
priority [1|2|3] - normal/elevated/priority fee
These are simply multiples of the default fee. That is,
priority 1 / normal fee is the default fee,
priority 2 / elevated fee is the default fee multiplied by 20, and
priority 3 / priority fee is the default fee multiplied by 166. This should be left to
normal currently, but might be convenient in times the blocksize is ramping up and blocks can be quite full. Bear in mind that the adaptive blocksize algorithm allows the blocksize to grow, but there could still be a few hours that blocks are somewhat "full".
It's fairly trivial to change them. If you want, for instance, to set confirmation for your transfers you have to type the following command into
set always-confirm-transfers 1
Similarly, if you want to turn it off:
set always-confirm-transfers 0