Sunday was Flag Day in the United States, a day commemorating a patriotic symbol full of sacrifice and varied emotions.

For many, the flag has recently been used as a way to rally against racism and police brutality.

"I think (the United States) flag has different meanings for everybody," said Robert Vélez, a political science lecturer at the University of Texas Rio Grande Valley.

The U.S. flag reminds him of his time in the U.S. Navy.

"My job in the Navy was to track submarines," Vélez said.

Although the flag reminds him of his service during the first Gulf War, for many others the flag is used a symbol to protest the problems they see within U.S. society.

Such as the case of NFL football player Colin Kaepernick, who initially would stay seated during the national anthem before games during the 2016 pre-season.

"And a veteran actually reached out to him and said, 'Hey, I understand that you're protesting, I fought for the right for you to able to protest,'" Vélez said.

That veteran was retired U.S. Army Green Beret Nate Boyer. He recommended Kaepernick take a knee instead.

Vélez said recent protests across the country showing outrage over George Floyd's death are similar to how Kaepernick was protesting against racism and police brutality towards black people.

After Kaepernick began kneeling, a national debate erupted with critics and supporters giving their views on what they considered disrespectful or not during the national anthem.

"The flag has always been a sort of a rallying symbol for Americans," Vélez said. "It's something that we can identify (and that) we're taught at a very young age"

It has also been a symbol used to unite Americans during tragedies and most recently, protests against racism.

On June 4, Saints football player Drew Brees apologized for his previous statements against football players kneeling during the national anthem, taking into consideration the current debate on police brutality and prejudices towards the black community.