No info on man-page, or on info-page for read command options

I'm new to Ubuntu.

I've read (I think) that man pages had all the information one would want... However, more often than not, I find commands whose man pages are left wanting.

Two examples:

• Command ls man page. If we read the -F option, then either we're already proficient, or we have no idea what's happening here. I had to look it up in the info-page.
• Command read. I've seen a script using read -p "string". Neither the man or info page seem to have any information on this.

I'm unsure whether I'm the one at fault for not being able to understand the information on these pages, or if there's really no useful info (for this context).

Any tips that help me improve my understanding skills of man pages are welcome.