ELI5 Asteroids - why NASA wants to catch an asteroid?

Explain asteroids vs comets vs meteoroids? An asteroid sample from the asteroid Bennu is now on its way back to earth (due in 2023) - why does NASA want to catch an asteroid and send samples back to earth? Did a meteorite kill the dinosaurs?

... We explain like i'm five!

Thank you to the r/explainlikeimfive community as always and in particular the following users whose questions and comments formed the basis of this discussion: neil1859, ultimateagentm, greenlandys, wayfareandwanderlust & mq7cqzsbk

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