An auxiliary used after the -masu stem of verbs or the stem of adjectives to indicate appearance or inference (meaning 'seems', 'looks like').
雨が降りそうだ。
It looks like it'll rain.
彼は忙しそうに見えた。
He looked busy.
この料理は辛そうだから、子供には向かない。
This dish looks spicy, so it's not suitable for children.
あの店のケーキはおいしそうだ。
The cakes at that shop look delicious.