Connects clauses or items, adding information or continuing a thought. Similar to それから or そして, but often implies a slight pause or shift. The gloss 'even so' is a possible contextual interpretation, not a core meaning.
See also: それとも
First do your homework, and then please clean your room too.
彼は優秀だ。それと、とても親切でもある。
He is excellent. Also, he is very kind.
そして is a neutral, general-purpose 'and' connector, whereas それと is less frequent and sounds a bit more deliberate when tacking on an extra remark.
それとも looks and sounds almost identical to それと but means 'or' (presenting alternatives), while それと means 'and also' (adding information).
Compound of それ (that) and と (and/with). The exact historical development is uncertain, but it functions as a conjunction derived from the combination of these elements.