Carrier oils are normally vegetable oils derived from the fatty parts of a plant, such as the seed, kernels or nuts; essential oils usually come from non-fatty areas such as bark, roots, stems, leaves and the aromatic portions of the plant
Carrier oils are not very potent or concentrated, this is to say they will not normally burn or irritate your skin if applied directly. Essential oils, on the other hand, are very potent and should never be applied to skin directly as they can burn right through it or cause very severe skin irritation! They have to be diluted in a carrier oil.
Lavender is one of the milder essential oils for skin but even then, direct application is NOT recommended.
Carrier oils are used for a wide variety of functions for skin and hair so even for regular usage a large volume is needed. As essential oils are highly potent you only ever need a few drops at a time. This is why they are sold in such minute volumes.
Carrier oils for consumer use are normally sold in clear, plastic bottles of 60 ml (2 0z ) at a minimum and frequently much larger volumes. Essential oils for consumer use are normally sold in 10 ml (0.35 oz) dark glass bottles.
Carrier oils don't easily degrade and evaporate. Essential oils degrade and evaporate rapidly when exposed to light; they also eat into plastic - this is why they are sold in glass bottles. That said, all oils should be kept in a cool dark place to make them last longer.
Essential oils are thin oils with strong aromas whilst carrier oils are thicker (more oily) and have a much milder aroma when they have one at all.
Top Carrier Oils For Hair vs. Top Essential Oils for Hair
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Carriel Oils (Wikipedia)
What Are Carrier Oils (Aromaweb)
Essential Oils (Wikipedia)