Rather depends who you ask. With all the recent controversy, actual historians have pointed out that a number of different flags were used by the confederacy for different purposes...There was a little-known-now "national" flag, several different "battle" flags, etc.
The one we are talking about is generally described as a "battle" flag and was normally used by military forces.
To diehard Southern sympathizers, the flag represents the Confederacy, the glory of resistance to the "War Of Northern Aggression", and so forth.
To less-radical types, it may simply be a symbol of their "heritage".....Of the brave soldiers involved in the war.
To black folks generally, it's a symbol of slavery, oppression, fear, and discrimination lasting long after the Civil War and up through the present. Including the era of "Jim Crow", segregation, lynchings, the Klan, and all that went along with the civil rights struggle.