What does indefinido mean in this context?

Hola Malcolm

I know, it's confusing because this tense does express actions that are "definite" - it has a long explanation that goes back to the classic Greek where they used this term of "indefinido". Here's a very useful video where there is a very thorough explanation of this. I hope you find it useful. She talks very clearly and slowly and it has subtitles. 

Saludos cordiales

Inma