As per the thread title, what does hair conditioner do?
I’ve got goddamned awful British-heritage hair that is dead straight, dull and now greying rapidly. For all the times I’ve used conditioner, I’ve never noticed any appreciable improvement in gloss or bounciness. 
What does it purport to do?
I have thick, straight hair that gets oily quickly and for me, the idea of conditioner is a joke. I think that “conditoning” is a controlled application of a uniform layer of some oily substance so that hair lays better, has more body, combs easier so conditoner may be important to people with dry or thin hair. When I tried some out of curiosity it felt like I had not washed my hair.
Thin hair person reporting in. Finally, a part of me that is thin!
Without conditioner, I cannot get a comb through my hair.
Conditioner smooths the cuticle (the outer layer of the hair that gets “rough” and damaged by heat, chemical processes and combing). The key ingredients that do this are a silicone, and/or a quaternium compound. They coat and stick to the hair, even after rinsing out the conditioner. It also adds “slip” (for detangling wet hair), and gives the appearance of less damaged hair.
In addition, conditioners are typically acidic, which will also help close up the cuticle after washing the hair with shampoo. Applying vinegar (acidic) before a final cool water rinse will achieve the same thing, if your hair cuticle isn’t that damaged. A smooth closed cuticle will reflect more light (i.e., shinier hair).
These products can build up on the hair and weigh it down, in which case you can use a “clarifying” shampoo to remove the build up and start over.
Pure coconut oil is one of the few oils that will actually penetrate the hair, so you can try that as a deep condition treatment, or applying lightly to damp hair as a leave in to add shine and smoothness.
If your hair is naturally stick straight, no conditioner I know of will make it “bouncy” on its own. I suggest a lighter conditioner so it’s not as weighed down (no silicones), and give the vinegar rinse a try to increase shine without weight.
There are also various mechanical methods (rollers, braiding while drying), heat (blow dry or iron), or chemical processes (perm, body wave) to add waves or bounce to your hair.
Unfortunately, hair usually loses moisture and shine with age (grays hold less moisture and have a rougher cuticle that reflects less light). 
I use it only for the detangling properties (and for shaving my legs if it is cheap).
I have thin, straight hair that is long. If I use conditioner on my head, it makes my hair look oily and flat, so I just use it on the long part (about neck down) to detangle for brushing.
since it is a cosmetic there are billions of products.
there are different types of conditioners doing different things. all empty your wallet.
some are some kind of fat.
Conditioner is designed to fool you when you get in a hotel room shower. You spend the day cursing that cheap hotel shampoo for leaving your hair all greasy.
Yep. However, my solution to this is to simply use cheap 2 in 1 shampoo. That works fine, but shampoo without the conditioner, it tangles, and I can’t comb it.
I wish that worked for me, I’d save so much money. My husband uses a 2 in 1 and I still find my hair is too tangly after. :mad:
Ditto. Totally.
My problem is that it is hard to find shampoo without conditioner. And when I do find it, it is labelled, “For dry hair” or “for thin hair” or “for normal hair”. There used to be a brand called “FOHO - For Oily Hair Only”, but it seems there aren’t enough of us to have kept them in business. I tried googling it, and found that the Dope already discussed this four years ago; click here.
It slimes up the shower and clogs up the drains.
Mix that with a long haired daughter and the shower becomes a lethal slip hazard and the drain is a scented but putrescent toxic waste dump.
When people say thick/thin hair are they talking about the density of the growth on the scalp or the size of the strands?
Keeve, are you in the U.S.? If so, Suave Daily Clarifying Shampoo is ubiquitous in any grocery, drugstore, Walmart/Target-type places, etc.
I was a little confused about your comment, though. ISTM that “plain shampoo” brands outnumber 2-in-1s decisively. Or is that “plain” shampoos have unadvertised “stealth” conditioning ingredients?
Anyway, I also have super-oily hair and have no need for conditioner at all. I get great results from the Suave. And it’s cheap, too (ignore that oddball Amazon price … it’s invariably under $2 if you buy it in a store).
I believe diameter of the strands.
I’m a big fan of the plain vinegar rinse. I haven’t used conditioner in years, and the vinegar rinse not only gets the residual soap out of my hair is also acts as a de-tangler.
Of course, YMMV.
It doesn’t do anything: that’s the beauty of it!
Neutrogena Shampoo, Anti-Residue Formula is also a really good shampoo to leave your hair squeaky clean. Unless your hair is really oily, it will strip it too much if you use it every day.
This is exactly what I use. But what does it mean to “strip it too much.” I have to admit, the language of hair care is mystifying to me.
It means “removes too much oil, leaving your hair dried out”. (Used to work in the hair care industry. 
)
And for us super-oily-haired folks, this is never a concern 
I’m actually curious to purposefully dry out my hair just once to see how it feels (I know from experience that Dawn dishwashing liquid, for instance, won’t dry my hair out a whit).
…
The Nutrogena shampoo suggestion is a good one – love that stuff, too.