What you need to knowThis Friday solemn tributes took place across the country, including Boston, to commemorate the 25th anniversary of the September 11 attacks.Near 3,000 flags cover Boston Common Park and each pays tribute to a person who lost his life on that fateful day 25 years ago.More than 200 people in Massachusetts died in the terrorist attacks.Two American flags have flown over the gateways to the B32 and C19 gates of Logan Airport fo…