ELI5 Ball Point Pens - why do the caps have holes?

Why do most pen caps have holes? When a pen quits half way through the word, why will it write on a fresh piece of paper but not over the letter it failed on? Why do some people call the ball point pen a biro pen?

 

... 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: smalltownmortician, sonderfrission, conspiratorm & capilot

For some cool science experiments to do with dry ice, check out this site: https://dryiceinfo.com/science.htm

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