Dry skin and dehydrated skin look similar but are different conditions with different fixes. Dry skin is a skin type (lacks sebum production); dehydrated skin is a state (lacks water content). Both can occur together.
How to tell the difference
Dry skin: produces less oil constantly. Skin feels dry hours after moisturiser. Often has fine flaking. Permanent skin type. Dehydrated skin: feels tight even when skin produces oil. May look 'crepey'. Skin can be oily AND dehydrated. Temporary state.
Fixes for each
Dry skin: needs occlusives (ceramide-rich creams, oils, balms). Avoid stripping cleansers. Look for ingredients like squalane, shea butter, ceramides. Dehydrated skin: needs humectants (hyaluronic acid, glycerin, urea) on damp skin, sealed with moisturiser. Address the cause (over-cleansing, dry air, dehydration).
Many users moisturise heavily and stay 'dry' because what they need is humectant-driven hydration, not more oil. Knowing which problem you have means picking the right product.