Fabric does most of the quiet work in how a garment behaves — how it drapes, how warm it feels, and how it holds up to being worn and washed. Knowing roughly what a fabric is made of, and how it is woven or knit, makes it easier to guess how a new piece will actually feel once it is on, long before the label is read closely.
Woven cottons and linens tend to sit close to the body but still let air move through, which is why they are so common in warmer-weather pieces. Linen in particular has a slightly textured, relaxed look even when pressed, and it tends to soften with wear and washing rather than losing its shape. Cotton is a little smoother and more consistent, which is part of why it turns up so often in everyday basics.
Knitted fabrics, by contrast, move with the body. A ribbed knit will hug closer, while a looser knit drapes and skims, which is why knitwear is so often reached for in layering pieces — a cardigan, a fine-gauge top, something that needs a bit of give. Knits also tend to be more forgiving of movement, which suits pieces meant for everyday, all-day wear.
There is no single best fabric — only a better fit for the occasion. A structured woven piece suits something tailored and considered, while a soft knit suits something easy and everyday. Paying attention to fabric, alongside cut and length, is one of the simplest ways to build a wardrobe that actually feels comfortable to live in.