selectInput selectOutput info

Dear all
I have to use the selectInput function on my sketch.
Unfortunately I can’t find a detailed description of it. I don’t understand, for example, how to direct the selectInput in a directory or how to use file filter as “*.txt”

Thank you very much for your help and cooperation

In addition to searching this forum and the old forum, there is the reference page – and keep in mind that you can also click through and find it in the JavaDoc:

…or even search the source code: