Pure Perfume Oil
Single-note oils like those bought in healthy food shops and aromatherapist suppliers aren't perfumes, they're oils that happen to smell nice. A pure 100 percent perfume oil made by a perfumer is rare and would almost certainly smell bad or, at least, not anything like itself. A perfume is a bit like trying to read a document in a zip file. The alcohol and water helps it to decompress and expand into something coherent and readable.
You might expect a solid wax of perfume oil to be highly concentrated or long-lasting but this isn't always the case as many seem enveloped in beeswax , paraffin or some other such thing. Others can be lovely, but what is true across the board is that these leave greasy stains on fine fabrics and attract lint from knitwear.
Perfume or Parfum
People will often describe perfume as 'stronger' even thought what they are saying is misleading. What perfume, parfum or 'extrait' is is the most concentrated juice, containing a higher percentage or perfume oils and aromatic ingredients. Perfume contains less alcohol than it dilutes. But non of this necessarily means a 'stronger' scent. Often, a perfume actually smells softer than it dilutes.
Eau de Toilette
A perfume concentration of about 10 per cent, EDT is substantially cheaper than perfume but will need to be resprayed at least twice a day to stay fresh, making it a dubious economy. EDT seems to smell a bit sharper and comes on strong but fails to hang around afterwards.
Eau de Parfum
EDP has around 15-20 per cent concentration of aromatic compound, which seems to be a good medium. It doesn't stain clothes as badly as other 'perfumes' will but lasts long enough to soften and develop well before it needs a top-up. It's less scary cost means that you can spray it until your hearts content without unduly forcing the scent onto others.
Eau de Cologne
It typically has a perfume concentration of about 5 per cent and smells citrus and crisp. Unlike the other dilutions, cologne rarely has a parent perfume and operates more as a scent unto itself. It's a fresh, fleeting and alcoholic formula that's hugely uplifting.