The mechanics behind penis pumps are really simple in concept. You start with an acrylic cylinder, insert a penis, and create a vacuum (hydraulic or pneumatic) to artificially draw blood into aforementioned penis. This results in an erection. The reason you find so much difference in price and design among pumps owes to the fact that while those basics are similar, construction and intended usage will vary quite widely. For the purpose of this overview, let’s group them loosely into Medical and Playline. Medical is crafted to specific standards, can detach at the pump to allow for freedom of movement once engaged (some can even be used with other types of pump cylinders, like nipple or vulva attachments), and will have a gauge to you can use to follow medical instruction. Hydromax, though it has no gauge, is also appropriate for medical use as the design prevents the possibility of over-pumping. Playline will have a lower price point, but will be less sophisticated in construction. That in mind, here are the four most common reasons I have found that people will reach for a penis pump.
Body Modification: When someone says the phrase, “penis pump” most think of body modification (specifically permanent enlargement). Though this isn’t the most common purpose in my own experience, it is the typical first thought. So, how is enlargement supposed to work? Drawing all that blood into the penis, more than it could normally contain, the spongy tissues and capillaries will hyper-dilate. In theory, stretching to top capacity repeatedly will, with time and repetition, cause that top capacity to increase. Does it actually work? It can, but not they way many expect. True lasting body modification requires time and dedication. You are looking at a commitment of many years for gains that are measured in quarters of an inch. I don’t say this to discourage would-be body modifiers, far from it! I just want people to be realistic about the process, so that they don’t give up before they have really begun. I would also strongly recommend reading up on safe levels of pressure and “work out” programs before this journey begins. Join a forum, while you’re at it, so you can get tips, warnings, and encouragement from others on the same path. Be safe and go slow.
Therapeutic: Most common among reasons for a medically prescribed pump are post prostate surgery or hormone replacement therapy to prevent atrophy. Much like an arm or a leg, if you can’t use it due to injury, you could loose mass over time. A pump can provide a means to maintain regular blood flow through the genitals when the body can’t do it alone. Many, many, times in my history on the sales floor, I have had men walk up to me with a literal doctor’s note detailing what type of pump he needs and his recommended usage schedule. I’ve never met one happy to admit why he is there,but I hold this person in great respect. There is no shame in following a doctor’s orders to keep the body working and healing correctly. This category can often overlap with the the next use, Erection Aid.
Erection Aid: (used in conjunction with a penis ring) There are myriad reasons why a person may want help 
getting a quick erection. Maybe a prescription medicine is interfering with the plumbing? Perhaps there were a few too many shots of liquor on a Date Night? Maybe a fellow had prostate surgery last year and, while physically healed, he is emotionally haunted and erections are unreliable. No matter the reason, physical or psychological, a pump can provide a quick and simple answer. As established, all a pump really does is induce an erection through external means. That us going to work no matter the condition of mind or body. Roll or snap a penis ring into place once the erection is achieved and you have a good half hour of playtime. (I specify a half hour because of the blood constriction aspect. Always take breaks when using penis rings!)
Masturbation: This use is my personal favorite, for obvious reasons. Why would a pump be part of masturbation or foreplay if you can get an erection on your own? First, the hyper-engorgement caused by a pump lasts for several minutes, even without a ring. With that comes increased sensitivity. The benefits to be found in that are pretty self explanatory. It also looks imposing, and that can be a turn-on in and of itself. Perhaps someone has an inflation fetish or wants to play out a medical scene? I will also mention that watching a penis go from 0 to 60 in two heartbeats is visually stimulation to an observing partner, regardless of those other added bonuses.
What to Avoid: Before you begin, become familiar with your device. Again, before a penis goes into a new device, even if you have had other pumps before, get to know the new one. Where is the quick release? How long does it take to get free? Can you detach the cylinder from the pump once you have the desired pressure, or does in need to remain attached? If it has a gauge, do you know how to read it. It shouldn’t pinch or hurt ever. Inspect for bruising or discoloration after use, just in case. (If you bruise, you’ve done it wrong.) Start with less and work up gradually, is not a competition. Don’t leave it on too long, either! This in not like the “15 minute rule” in a hot-tub where you laze in there for two hours and are fine. You really do need to watch your time and take breaks. 5-10 minute sessions are best, but you are free to repeat once your body has rested.
