Maknae means the youngest member in the group :D, some people think its Sunny but its Seohyun!! ^^
And as for aegyo, its just something like cuteness? Like how people say Sunny has lots of aegyo, its usually because she acts so cute all the time xD But it doesn't mean cute, just that you have this cuteness about you? I'm not sure how to explain clearly lol, but yeah. Maybe something like charm/innocence, or someone's sweetness or cuteness.
Maknae which means the youngest (in SNSD wld be SeoHyun) and Aegyo which means there cutness (in SNSD wld be Sunny)... for ex. when somone is asking u to do/show "aegyo" means to show some of your cutness.