Same as "I agree"

When someone goes to the gym and spends 90% of the time on their phones scrolling through social media

A 16 year, old ska-rock-new wave, band that was formed in the late 1980s in Orange County,CA. The band members are Tony Kanal, Adrian Young, Tom Dumont, and Gwen Stefani. After the release of their first album No Doubt's Gwen and Tony broke up. While in production of their following album(Tragic Kingdom) Gwen wrote many heart-breaking songs about Tony. No Doubt's break through album was Tragic Kingdom in 1995! They have been releasing more albums ever since and their most recent work is The Singles 1992-2003.This great talented band performed at The Super Bowl in 2003 with Sting and is still together to this day. No Doubt has won many awards such as MTV VMAs, RMAs, a Grammy, and many more. They have been around for a long time and will be around for much longer.

A reply to a statement you agree with.
-for sure
-no lie
-Amen

Talented band whose first album most CERTAINLY was NOT Tragic Kingdom. Sheesh. Get it right, kids.

One of the best bands ever created. No Doubt has gone through many ups and downs and has acomplished alot. They have even earned the key the city of aneheim. Adrian Young, Gwen Stefani, Tom Dumont & Tony Kanal is No Doubt.

literally, it means that there is a lack of any ambiguity.

it is used in the same way as "i agree" or "yes"