Speaking of toys men like to use to get their rocks off... Pumps are pretty popular, too. There are so many available out there - it's enough to make your head spin. The original purpose was to help post-prostate surgical men achieve erections; though available over the counter in a pharmacy, they would be prescribed by the surgeon (or urologist). Somewhere along the line, guys noticed the difference in the length and girth of their cocks right after pumping up. Most guys do use them to make their cocks bigger - it's a temporary gain unless used repeatedly for many, many months.
What they do is draw more blood into the cavernosum, stretching and bloating them to maximum extent.
Alone, or with a buddy or two, they can be a lot of fun - I've had a couple in the past, just to play with and pump one out from time to time.
I think an equal number of men just like using them to play and jack off. Guys should be cautioned when playing with these things though... They have been known to cause damage to the dick if not used with the proper care. The Tunica can tear; if not enough lube is used, the skin of the shaft or foreskin can tear.
Go for it if you enjoy it but, as always, The Whackman asks you to play safe!
Yes, ladies, it's perfectly fine to add them into play with your guy ... as long as you never, never, ever have made any comments about the size of his cock.