Five symbols, in order. Every care label runs the same sequence left to right: a tub (washing), a triangle (bleaching), a square (drying), an iron (ironing) and a circle (professional cleaning). Learn the shapes and any label in the world becomes readable.
The tub is the one you'll use most. A number inside is the maximum wash temperature; a hand in the tub means hand wash only; a bar under the tub asks for a gentler, reduced-spin cycle and two bars for the gentlest of all. A cross through the tub means do not wash it in water at all.
Dots mean heat, everywhere they appear. Inside the iron and inside the tumble-dry circle, dots indicate how much heat is safe — one dot is cool or low, two is medium, three is hot. More dots, more heat. A cross over the symbol always means don't: a crossed tumble-dry circle means air dry only.
The square is drying, the circle is the dry cleaner. Lines inside the square tell you how — a vertical line for line-drying, a horizontal line for drying flat (which is what all your knitwear wants). The circle is for professionals: a letter inside tells the cleaner which solvent to use, and a crossed circle means it can't be dry cleaned. When symbols and instinct disagree, follow the label — it reflects the weakest component in the garment, be that a glued interlining or a delicate trim.